Can not install add-ons since Firefox upgrade

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.

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

Please check the issue.
Thank you.

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