Well, you are on Windows and BLE support there is a bit more hit and miss.
Please read the user manual about forgetting the device and re-pairing it using Windows system tools.
Only when Subsurface can "see" the device in the "Choose Bluetooth..." dialog is there a chance for this to work.
And yes - this is a somewhat frustrating experience - but usually once it works, it keeps working.
(in general, I prefer downloading from BLE only dive computers on Android or iOS and using the cloud to transfer the dive data to a computer... there are just too many things that can go wrong on Linux, macOS and especially Windows)
/D