There is no difference in the installer for Xeams Community and Enterprise Edition. It will run as if you have purchased the Enterprise Edition for the first 30 days. It will then get converted to Community Edition unless a license is purchased.
After a few hours I eventuially found it:/opt/Xeams/config/sslCertHosts.datThis file had:mta-sts.BLAH.netmta-sts.BLAH1.commta-sts.BLAH2.commta-sts. Removed the last entry, restarted Xeams and renewed the Let's Encrypt certificate finally.