Pairing unsuccesfull - iPhone can no longer connect to "Bose TV Speaker". Forget this device and pair it again

Hello there,

I'm getting this error when I'm trying to connect to my Bose TV speaker via bluetooth on our iPhones & iPad:

Pairing unsuccessful - iPhone can no longer connect to "Bose TV Speaker". Forget this device and pair it again

Not working on the devices:

iPhone 12 mini, iOS 15.0.2

iPhone SE (2nd gen) , iOS 15.0.2

iPad Air 2 , iPadOS 15.0.2

Working on:

iPhone 8, iOS 15.0

Steps taken:

1)iPhone/iPad restarted

2)Bluetooth re-enabled

3)TV speaker's firmware updated

..and still not successful.. Could you please help & advise?