I have this same issue with one domain name on a server that is chock full of other domain names that use GeneratePress. I know it’s an hosting issue, but I don’t know what to tell them to look for.
I suspect it’s an issue with the new generic tlds for me, because I had odd issues running up against rules that the host needed to whitelist with other new tlds.
Can you look and see what I should maybe tell them? Sending you email with a login.