I think you posted in the wrong community my guy

Their staff posted on their Reddit channels that it’s a limitation of their billing system, I believe in relation to having two different services at once. They said they’re working on updating the billing system to support this but I don’t recall an ETA.

I think you’d have to create a second account currently, but then you may lose access to the introductory pricing to Proton Pass if later you wanted to move back.