Screenshot of the error

This could occur if there is a failure during the certificate check -- all add-ons need to pass a signing certificate check in order to install.

Could you double-check your system date and time? There is an allowance for some discrepancy, but a large discrepancy could cause this problem.

Looks like this extension hasn't been re-signed and use the new certificate done earlier this year. I'm not sure whether this still will be done.

• https://discourse.mozilla.org/t/upgraded-add-on-signatures/129599

Note that this extension was last_updated: 2018-01-28T05:20:11Z

Looks like this extension hasn't been re-signed and use the new certificate done earlier this year. I'm not sure whether this still will be done.

• https://discourse.mozilla.org/t/upgraded-add-on-signatures/129599

Hmm, I wonder what happened with the re-signing. It was automatic for my oldest extension. ??

Could you double-check your system date and time? There is an allowance for some discrepancy, but a large discrepancy could cause this problem.

The first thing I want to say is, thank you so much for the answer. I checked the system time, the clock is 0.5 seconds behind, but I think this is within the norm, because the OS itself sets the time automatically. The date is accordingly normal.

Note that this extension was last_updated: 2018-01-28T05:20:11Z

Yes, I noticed that. But even after installing the latest Firefox update, I could use the add-on without any problems. But if you delete it, you can't install it anymore. The only solution I could find was to install the extension as a temporary one, in this case it works even though it issues a warning. I'll try to install an older version of Firefox.

I installed the ESR version of Firefox 115.13. The add-on came straight from the store. There is an assumption that in the latest versions of the regular version, edits were introduced, which is why it now gives an error

Note that once the extension has been installed via 115 ESR, it might keep working if you upgrade the profile to the current release.

Note that once the extension has been installed via 115 ESR, it might keep working if you upgrade the profile to the current release.

Thanks for the answer, though, since the regular version of firefox is still newer than the latest ESR build, I couldn't transfer my profile to it. Therefore, I went the opposite way, installed Firefox Nightly and already disabled the verification of add-on certificates there, moved my main profile and everything works like clockwork. The only thing is, I don't really like the daily updates of Firefox Nightly, I think to disable them, because it is possible that in the next update they will break my browser again and it will no longer be possible to transfer my profile.

I think we need to figure out if it is possible to transfer the profile to an older version, but for now I will be satisfied with the current solution