User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36

Steps to reproduce:

Select my calendar tab, click Synchronize.

Actual results:

A small error (?) window pops up with no message or title.

Expected results:

It should have sync'ed with the google calendar server. It was working fine up until 2-3 months ago.

I forgot to attach my application basics from the troubleshooting menu. Attached here.

Sounds like a duplicate of bug 1541304.

What happened 2-3 month ago?

(In reply to WaltS48 [:walts48] from comment #2)

Sounds like a duplicate of bug 1541304.

What happened 2-3 month ago?

The behavior as far as the error message is similar, but the error that pops up in the error console is not. I would have posted earlier, but I just found the error console. This is what comes up when I click the synchronize button:
SyntaxError: redeclaration of var cal
calendar-conflicts-dialog.xul:17:1
<anonymous> chrome://calendar/content/calendar-conflicts-dialog.xul:17
promptOverwrite resource://calendar/modules/utils/calProviderUtils.jsm:338
promptOverwrite jar:file:///C:/Users/Bill/AppData/Roaming/Thunderbird/Profiles/7btjfm5t.default/extensions/{e2fda1a4-762b-4020-b5ad-a41df1933103}.xpi!/components/calDavCalendar.js:579
onStreamComplete jar:file:///C:/Users/Bill/AppData/Roaming/Thunderbird/Profiles/7btjfm5t.default/extensions/{e2fda1a4-762b-4020-b5ad-a41df1933103}.xpi!/components/calDavCalendar.js:812
onStreamComplete self-hosted:993
oauthCheck jar:file:///C:/Users/Bill/AppData/Roaming/Thunderbird/Profiles/7btjfm5t.default/extensions/{e2fda1a4-762b-4020-b5ad-a41df1933103}.xpi!/components/calDavCalendar.js:355
oauthCheck self-hosted:1037
ReferenceError: onLoad is not definedcalendar-conflicts-dialog.xul:1:1
onload chrome://calendar/content/calendar-conflicts-dialog.xul:1
promptOverwrite resource://calendar/modules/utils/calProviderUtils.jsm:338
promptOverwrite jar:file:///C:/Users/Bill/AppData/Roaming/Thunderbird/Profiles/7btjfm5t.default/extensions/{e2fda1a4-762b-4020-b5ad-a41df1933103}.xpi!/components/calDavCalendar.js:579
onStreamComplete jar:file:///C:/Users/Bill/AppData/Roaming/Thunderbird/Profiles/7btjfm5t.default/extensions/{e2fda1a4-762b-4020-b5ad-a41df1933103}.xpi!/components/calDavCalendar.js:812
onStreamComplete self-hosted:993
oauthCheck jar:file:///C:/Users/Bill/AppData/Roaming/Thunderbird/Profiles/7btjfm5t.default/extensions/{e2fda1a4-762b-4020-b5ad-a41df1933103}.xpi!/components/calDavCalendar.js:355
oauthCheck self-hosted:1037

I've found in add-ons that it states TB v67 is not compatible with the Google calendar provider. Have removed that, and will try re-configuring via lightning if I can.

Okay, so looking at versions, it appears that my issue is that neither lightning or google calendar provider will work with v67. That seems like a non-starter for many people. Beta-testing hazzard. The question then, when is the next beta release, and what will it support?

Lightning 6.9 is the correct version for TB 67.0b3.

Provider for Google Calendar can be found from the link in the release notes. The 2nd unresolved known issue from the bottom.

TB 67.0 Beta Notes

Although you don't need it if you setup a Google CalDAV calendar.

Next beta release should be soon and as always the correct version of Lightning will be bundled with it.