Thank You for the feedback. The "certificate not found" is a generic error message from the Firefox web browser, not Web eID, which indicates that certificates aren't transferred to the web browser. Most likely the error is related to the Firefox snap issue https://bugzilla.mozilla.org/show_bug.cgi?id=1734371,where it is recommended to use the regular Firefox web browser instead. If that isn't the case, we would recommend contacting ID-helpline https://www.id.ee/en/article/notify-us-of-the-problem/.