Can not install add-ons since Firefox upgrade

Hello.
I have installed an add-on using a GPO.
However, after upgrading to Firefox 68, my add-on is getting an installation error.
Is it impossible to install by GPO on Firefox 68? If not, why is not it installed?

The following is the part I checked about by connecting to about:policies.




Installation via download, not GPO, is installed normally, below is the installation link.
https://addons.mozilla.org/firefox/downloads/file/3365031/gradius-7.3.11-fx.xpi?src=devhub

In the case of GPO installation, my add-on as well as other add-ons are not installed.

Please check the issue.
Thank you.

For help in Enterprise settings, please visit this page: https://support.mozilla.org/en-US/products/firefox-enterprise