Add-ons/Extensions are not visible in the installed list

In Menu Tools/Add-ons/Extensions tab doesn’t have a list of installed extensions (see below). Even they there are active, as seen on right side - pdf edit, translator, adblocker, etc.
Where did he disappear? Can I get some hidden backup?
Or is it a issue with some new version of FF? I have ESR 52.4.0_32bit (czech version)
thx for any advice
Peter

This is either a strange bug in Firefox, or it could be that those add-ons are intentionally hiding themselves from the add-ons list (which could mean they are malicious).

Some things you could try:

  • Install an add-on from https://addons.mozilla.org/ and see what happens.
  • Look in about:support to see if they appear in the extensions list.