here are couple of possible scenarios why this is happening.
1. exceeded paired device number at the same time for the speaker category in the bluetooth device
2. exceeded paired device number at the same time for the speaker category in the phone itself
Try to remove all the devices in the list from the bt device and phone and pair them together again.
hopefully this works.
If nothing works, then factory reset of the phone or exchange....
Samsung just needs to fix this issue. Never had any problems with my Note 5 and Android 7.1. Starting to think I made a mistake paying the over inflated price for a phone with reduced capabilities.
This seems there's a change that the developers in Samsung need to be notified about whether it's Oreo as an issue or the hardware in the s9s architecture due to the upgraded chip 845 in it.
Bluetooth receiver appears on scan but does not pair or ask for code.
I got my JBL speaker to pair. .I just reset the speaker. .Did nothing on phone .. I reset speaker using Bluetooth button and power button. On off then Bluetooth button. Then poof it showed up in s9 plus. Finally !!