Redirect error when connecting to Stripe

I’ve set up a payment showcase for stripe. It’s been working for ages, but has stopped working in about September. I get this error:


Please forward this error screen to’s [WebMaster](

Access is forbidden to the requested page:[sessionId]&key=[key] (port 443)

I have been trying to find something but I’ve not found anything. I’ve upgraded the stripe API, upgraded the UMP wordpress plugin to 12.4 and nothing works. Funny enough, I am using another UMP plugin for a similar site and connecting to the same stripe account, and that works fine.

Anyone know how to fix this?

This is beyond of helping and providing free support for the item by the author.
If you’re looking for paid support, it’s another case.