Question ARFoundation camere freez after ad (AdMob)

Hello. I have an application where users can add more than one AR model to the ground.
App flow is this. :
1. Open Model List
2. Select one
3. Place on the ground
4.Press "ADD/PLUS" button
5. Select another model
6. Place on the ground next to the previous model.

Some of the models are unlockable with ads. So when you selecting a model with an ad (on step 5), after watching the ad Step 6 starts, but the AR Camera is freeze. I can still interact with the model but the camera background (my real space) is freeze.

What can be the problem?
This problem happens only on IOS. Andoird works fine.
Thanks.