Created attachment 8651928 [details] thunderbird-calendar-about-config.png User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:40.0) Gecko/20100101 Firefox/40.0 Build ID: 20150812163655 Steps to reproduce: Launch Thunderbird 38.2. Actual results: It's gone. My calendar tab disappeared. ...So did all of the relevant menu items to bring it back, like "show Today pane" "show calendar" etc. (Just doing those from memory, so they're probably not verbatim what used to be there.) There's also no mention of calendar in the options window. The only local proof that I'm not delusional (I swear I used to have a calendar!) is the two dozen calendar entries in about:config. Screenshot of that, here http://i.imgur.com/KGUY77k.png (and attached to bug report) The calendar keyboard shortcuts also don't work. I should note that I've already uninstalled and reinstalled TB, to no avail. Windows 7, fully updated, running on a beefy machine. Expected results: Calendar tab should be there. If not, menu and/or keybd shortcuts could bring it back. Alas, not my lucky day.
That was quick. I was under the impression that Lightning was now integrated into TB. Poking around a bit, I found that Lightning still exists as an addon. Downloaded 4.0.2 and installed it. Calendar back. Easy. Wonder why it uninstalled.
In general, this is a valid report, because it shouldn't have disappeared after TB update. Installing from AMO is just a workaround. From which version did you update to TB 38.2? Was Lightning completely uninstalled or still visible but disabled in the add-ons manager? Based on the config screenshot, you use the default Home calendar and a Google calendar using the Google provider, correct? Has this been uninstalled, too, or just disabled when updating to TB 38.2? Are there any other noteworthy infromation about your installation like not common profile locations, running the installation with administrator priviledges, installation via software distribution etc.?
99% sure I did not manually update, so it was almost certainly incremental from whatever was the previous release. I neither uninstalled nor disabled Lightning prior to the upgrade. I do not "use" the Google calendar, though apparently I haven't totally removed it from config. Deprecated years ago. I do not see it in the sidebar, where I only see: Calendar [x] Home (Long ago, the other calendar used to show up here too, but it's been years since I used it.) Profile is not on the OS SSD, but is on a data SSD, other than that, file locations are pretty standard, I think. Of note: I found a thread wherein many other people had this same problem. https://support.mozilla.org/en-US/questions/1078257 You might post there to ask for additional information. Let me know if you need anything else.
This may have been another report for the sync issue in bug 1211160, fixed for TB 38.6.0 - do you still expirience this bug for that recent version?
I re-installed lightning and never had this problem again.
Thanks. Resolving WFM as per comment 5.