I have Thunderbird with Lightning that I use for work. I have several calendars set up in Lightning (local, google, and Exchange) which each have a different purpose, and have all been working together happily for two and a half years. Yesterday, Thunderbird upgraded to v52.1.1 and on boot upgraded my plugins as well, and now my Exchange calendar (via Exchange EWS Provider 3.8.0-beta2) will not synchronize at all. I deleted the Exchange calendar with the intention of re-creating it - but now there is no communication between Lightning and the company Exchange server so I can't recreate the link at all. Thunderbird is still talking to the Exchange server perfectly (via ExQuilla) so e-mail communication is not affected. This also proves both the server, account and password are still intact and working. I CAN still use the company's web version of outlook to access both e-mail and the calendar, so I know that system is still working from the server side. I don't know if the issue is with Thunderbird, Lightning or Exchange EWS Provider, but it is a royal pain only having two of my three calendars available in TB, and having to use a web version of Outlook to access the third. Company security policies prevent me using an alternative to the Exchange server for company events so I'm a bit tied to it... I note several others are reporting the same issue on github. Does anyone know of a solution to this? Thanks in anticipation.