I hadn’t even made a single transaction before I got banned, so presumably there was something about my email address, phone number or postal address they didn’t like. I was registering in the UK with all UK details etc. something tripped, but I have no idea what. Upon contacting PayPal’s executive complaints team using details I found on Reddit they decided to do a whole bunch of KYC and reverse the ban, but they were adamant that it was irreversible when I initially contacted them using their normal phone number.
To this day I have no idea why (and it wasn’t clear to me that the complaints people even knew), just that something flagged in their automated system.
There are always false positives with this kind of thing, and you can only hope that you don’t become one. I’m lucky that it was possible to fix my issue but as automated decision making becomes more common there will be increasingly large numbers of people who are just arbitrarily denied access to services with absolutely no recourse.