I have been a Thunderbird user for many years and am on the release update channel. My calendar tab disappeared when I updated to version 68. I have followed the steps outlined in re-setting Lightning to no avail. I have verified that Lightning is version 68 also. The google calendar addon is version 68 also. Not sure where the problem lies or how to fix it but not having my calendar tab is a show stopper for me.

Any help would be much appreciated.