Bluetooth cannot be activated on Xperia XA2 Ultra running Sailfish 4.0.1.48 (Koli)
Restarting the phone didn’t help and only after restarting bluetooth and bluebinder it worked again.
Found in Sailfish OS Forum
Enable developer mode, use the terminal or ssh to your device
devel-su
systemctl restart bluetooth.service
systemctl restart bluebinder.service