Hey @Michiel_Verfaillie, the issue actually popped back up a few days later so it wasn’t a real fix. It appears the problem has something to do with an ‘open’ session on another device. Eg. Zwift is still running in the background of your phone and you open Zwift on your computer.
My fix: I deleted the apps on all my devices, including any files left even after deleting the app on my MacBook. That worked - and Zwift support told me to be very careful not having Zwift open on multiple devices.
I now rarely use my MacBook for Zwift, just an iPad or iPhone.
I hope this fixes your problem. Hit me up if you need more info - I know how frustrating this can be.