Web-ext fails to create "web-ext-artifacts" folder

I have recently succeeded in porting a Chrome extension to Firefox. I now wish to update it. I am keeping the new version in a separate folder on my local computer (MacOS 10.13.6). I ran web-ext once to create a zip file to submit, but AMO complained that it was the same version number as before when I tried to upload it. I then tried to repeat the procedure after removing the “web-ext-artifacts” folder. web-ext indicates success but no new “web-ext-artifacts” folder is created. I have emptied the trash, moved my files to a different folder and repeated but no new “web-ext-artifacts” folder. What am I doing wrong? Below is the verbose transcript of the last web-ext session.

Dans-MacBook-Pro:mentiplus f Dan$ web-ext run --verbose
[program.js][info] Version: 4.3.0
[program.js][debug] Discovering config files. Set --no-config-discovery to disable
[config.js][debug] Discovered config “/Users/Dan/.web-ext-config.js” does not exist or is not readable
[config.js][debug] Discovered config “/Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/package.json” does not exist or is not readable
[config.js][debug] Discovered config “/Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/web-ext-config.js” does not exist or is not readable
[cmd/run.js][info] Running web extension from /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f
[util/manifest.js][debug] Validating manifest at /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/manifest.json
[extension-runners/firefox-desktop.js][debug] Creating new Firefox profile
[firefox/index.js][debug] Running Firefox with profile at /var/folders/h4/1bp30c6n3wd6b5y4nj33sk0h0000gn/T/7f0baee6-be07-4feb-bf92-db1c74b2159b
[firefox/index.js][debug] Executing Firefox binary: /Applications/Firefox.app/Contents/MacOS/firefox-bin
[firefox/index.js][debug] Firefox args: -start-debugger-server 64035 -foreground -no-remote -profile /var/folders/h4/1bp30c6n3wd6b5y4nj33sk0h0000gn/T/7f0baee6-be07-4feb-bf92-db1c74b2159b
[firefox/index.js][info] Use --verbose or open Tools > Web Developer > Browser Console to see logging
[firefox/remote.js][debug] Connecting to the remote Firefox debugger
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/remote.js][debug] Retrying Firefox (0); connection error: Error: connect ECONNREFUSED 127.0.0.1:64035
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/remote.js][debug] Retrying Firefox (1); connection error: Error: connect ECONNREFUSED 127.0.0.1:64035
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/remote.js][debug] Retrying Firefox (2); connection error: Error: connect ECONNREFUSED 127.0.0.1:64035
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/remote.js][debug] Retrying Firefox (3); connection error: Error: connect ECONNREFUSED 127.0.0.1:64035
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/remote.js][debug] Retrying Firefox (4); connection error: Error: connect ECONNREFUSED 127.0.0.1:64035
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/remote.js][debug] Retrying Firefox (5); connection error: Error: connect ECONNREFUSED 127.0.0.1:64035
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/remote.js][debug] Retrying Firefox (6); connection error: Error: connect ECONNREFUSED 127.0.0.1:64035
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/remote.js][debug] Retrying Firefox (7); connection error: Error: connect ECONNREFUSED 127.0.0.1:64035
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/index.js][debug] Firefox stdout: Started devtools server on 64035
[firefox/remote.js][debug] Retrying Firefox (8); connection error: Error: connect ECONNREFUSED 127.0.0.1:64035
[firefox/remote.js][debug] Connecting to Firefox on port 64035
[firefox/remote.js][debug] Connected to the remote Firefox debugger on port 64035
[firefox/remote.js][debug] installTemporaryAddon: {“addon”:{“id":"mentiPlus@example.com”,“actor”:false},“from”:“server1.conn0.addonsActor2”}
[firefox/remote.js][info] Installed /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f as a temporary add-on
[cmd/run.js][info] The extension will reload if any source file changes
[util/file-filter.js][debug] Resolved path /*.xpi with sourceDir /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f to /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f//.xpi
[util/file-filter.js][debug] Resolved path **/
.zip with sourceDir /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f to /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f//*.zip
[util/file-filter.js][debug] Resolved path /. with sourceDir /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f to /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/
/.*
[util/file-filter.js][debug] Resolved path /.*//* with sourceDir /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f to /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/
/./*/
[util/file-filter.js][debug] Resolved path /node_modules with sourceDir /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f to /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f//node_modules
[util/file-filter.js][debug] Resolved path /node_modules//* with sourceDir /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f to /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f//node_modules//*
[util/file-filter.js][debug] Ignoring artifacts directory “/Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/web-ext-artifacts” and all its subdirectories
[util/file-filter.js][debug] Resolved path /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/web-ext-artifacts with sourceDir /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f to /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/web-ext-artifacts
[util/file-filter.js][debug] Resolved path /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/web-ext-artifacts//* with sourceDir /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f to /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f/web-ext-artifacts//*
[watcher.js][debug] Watching for file changes in /Users/Dan/Documents/Data/Firefox extensions/MentiPlus/4.1.1/mentiplus f
[extension-runners/index.js][info] Press R to reload (and Ctrl-C to quit)
[firefox/remote.js][debug] Received “end” from Firefox client
[firefox/index.js][debug] Firefox closed

web-ext run does not create an XPI. web-ext build will create an XPI for uploading to AMO. Note that you will always have to bump the version in the manifest.json whenever you upload a new version to AMO.