Thank you for your interest in Telerik Test Studio.
The only extension that is not signed is the Exploratory Testing Extension. Playback and Recording extensions are signed and working fine. Probably there was a newer version of the extensions and after upgrading your browser you had to upgrade them as well.
Currently there is no estimation time when the Exploratory Extension would be signed.
Please let me know if you need further information on the topic. Hope to hear from you soon.