Lightning TSL error after upgrade to 38.1 / 4.0.1.2

[HermieSoft]

Hello,

After upgrade TB to 38.1.0 the calendar isn't updating anymore.
Server = Communigate Pro 5.4.5
TB 38.1
Lightning 4.0.1.2
Location of Calendar = https://192.168.13.1:9100/CalDAV/herman (or external IP etc. give no changes)
The log of the server returns
The error we get
10:44:05.569 5 HTTPU [0.0.0.0]:9100 <- [192.168.13.73]:49673 connection request. socket=107
10:44:05.569 4 HTTPU-198052([192.168.13.73]) got connection on [192.168.13.1]:9100(re-tech.nl) from [192.168.13.73]:49673
10:44:05.634 3 HTTPU-198052([192.168.13.73]) failed to accept a secure connection for 're-tech.nl'. Error Code=TLS alert record received
10:44:05.634 4 HTTPU-198052([192.168.13.73]) closing connection
10:44:05.634 4 HTTPU-198052([192.168.13.73]) releasing stream

With TB 31.7.0 and Lightning 3.3.3 all works ok
Thanks in advance

[ssitter]

I think the Mozilla team changed a lot with regard to secure communication between 31 and 38. Like dropping support for some weak encryption protocols. Maybe your server is using of the no longer supported ones and therefore the connection fails? Have you checked Thunderbirds error console? Maybe there is some message. And maybe try to access the server from Firefox in case Firefox gives a more useful error messages?