This is about the new testing version 3.2.14, got the SSL working 100% on all servers, many thanks to Centova support for the help!
We have some resellers that use custom sub domains for their clients to use which does work, but not with SSL.

From Centova support ...
Once you have successfully set up let's encrypt, you can add more domains to your certificate, by manually modifying "/usr/local/centovacast/etc/ssl/domains.txt". Additional domains, must be added in the same line, separated by a blank space.
Centova Cast should automatically issue the new certificate, the next time the cronjob task runs. However, if you wish to force the update immediately, you can run the following command via the SSH console on your server.
/usr/local/centovacast/sbin/letsencrypt renew


The 2nd domain has been added to to domains.txt with a space between the 2, and when I run the cron I get

[root@li127-12 ~]# /usr/local/centovacast/sbin/letsencrypt renew
Account admin@server1.domain1.com server2.domain2.com is not registered. Use 'run' to register a new account.
[root@li127-12 ~]#

and of course the automated cron didn't work either

This is the guide I followed to install SSL
https://centova.com/doc/cast/installation_manual/08_Configuring_SSL
---- first you have to switch over to the testing version then update
https://centova.com/en/faq/cast3/information/access_to_test_releases

I THINK this is what Centova uses to issue SSL certificates https://github.com/dehydrated-io/dehydrated