Ixpand not being detected iPhone 6s ios 9.1

The device fw is up to date and it works on iphone 6 ios 11 but not on a iPhone 6s ios 9.1

I do not want to upgrade ios 9.1 to ios 11.

Is this a ios issue?

I tried everything. Erasing app restarting phone etc not working and very disappointed.

Is there a fix? Or do i return for refund

iOS 9 is pretty old. Probably best to update the iOS.