We have verified that there was an issue (on Cloudways end) with the update of the Let’s Encrypt older root certificate (DST Root CA X3) to their newest version (ISRG Root X1), which is causing some sites not to be able to connect to their MainWP Dashboard.
Cloudways is currently working on a fix, and we do not have an ETA.
You can watch CloudWays status on the problem at https://status.cloudways.com/
This issue may affect other hosts, too, but we only have confirmation from Cloudways.
Information on the Let’s Encrypt change can be found here: DST Root CA X3 Expiration (September 2021) - Let's Encrypt