Hi James,
Thanks for reporting the issue, apologies for the inconvenience caused! Today we discovered a compatibility issue between <4.0 add-ons and Really Simple SSL 4.0.4.
Did you have an older add-on for Really Simple SSL with 4.0.4 active? If that is the case, updating to 4.0.5 should resolve the issue.
Let me know if that was your issue as well!
Hi @thooghun,
Closing this as it should be resolve with the latest update, please let me know if you have any further questions!