Smartwatch won’t connect via bluetooth anymore

My mom tries to #bluetooth pair her smart watch and her phone. But every time she enters the correct validation code in her phone, the watch denies the #pairing.

- her watch is a Suunto Peak 9 Pro
- Smart phone is some Shift Phone 5 on Android 10
- watch and phone have been factory reset
- app has been reinstalled
- watch to the latest firmware
- phone bt cache and data have been deleted
- phone network data has been reset
- the watch *can* connect to other phone
- her phone "can* connect to other bt devices

Any suggestions? What are we missing?
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