Hi @Jeroen_Wigard welcome to Zwift forums.
Shuij at Zwift HQ here. I looked at your server logs for clues.
Regarding your Zwift Play controllers - they are still using the firmware version 1.0.0. Updating to the latest version 1.3.1 should make them behave correctly. Follow the links for instructions.
Regarding your Polar Vantage 3: did you update the fimrware recently? Polar’s release note for v 4.1.5 says "live heart rate broadcasting is no longer enabled by default for any sport profile" so you may need to enable that manually for Zwift to see it?
Please let us know if those two things solve your issue?