Is the base url set somewhere? Config files, etc?
Yes, base URL set as https:// in _ss_environment
Not so much 🤔 Maybe that is the problem?
It shouldn't be. It would usually only be a problem if there was one forcing a direction with http
Have you added
Director::forceSSL() in the config?
hmm.. I'm assuming it was in 3.1.. I can't remember that far back!
It might be worth a try
SSL was not an issue at all on a 3.7 site so I’m just wondering if SS was not that much into SSL in 3.1, 3.3 and so on. Which I find weird