On 08/03/2019 10:50, micky wrote:

Well, so far, no luck. It actually asked my phone for the code,
suggesting 0000 and 1234, but neither worked.

Yes, I've seen that too. What seems to fix it is on each device to
remove or forget the other, then try to pair again, and then the
originating devices creates and displays a key, and the target device
throws up a popup displaying that key and asking whether it is correct.