AR issues (two Samsung Smartphones)

Dear people,

I have a weird issue:
I have two Smartphones: Samsung Galaxy A5 and Samsung Galaxy S9+.

Previously AR worked for the both phones within the Sketchfab App. Since some time it works just for Samsung Galaxy A5, in S9+ it isn’t even presented with [AR] sign (I checked the same 3D-models on both phones).

I tried everything with S9+ (my ARCore is on the newest Google Play stand), still: on this device it doesn’t work. I’d love to use Sketchfab with S9+ since it has better processor and bigger display.

Do you have any idea, what could be the issue? And why the weaker Samsung supports AR, others than the better one.

Thank you,
best
Merzmensch