After having to erase my iPhone and start from a clean install, I downloaded the Revolut app. Entered my phone number and PIN, and kept getting errors (wrong PIN, which is not possible). Eventually, the system seemed unable to recognise my identity and apparently, created a new, duplicate account instead, with no data from my original account, and no ability to link my existing Revolut card.
Note: the Revolut SIM card used for activation/login was not inside the phone, as I am abroad and using a different number. But I kept entering the activation/login number as it is the one linked to my account.