Mullvad not conecting on iPhone (android hotspot)

Heiii team

I have an Oppo a16s serving as a hotspot to an iPhone with mullvad vpn,
since upgrading my Oppo to android v13 i have lost internet connection on my iPhone (16.4.1) when mullvad is on.

Can you guys help? If not do you have a guide on downgrading to android 12?

Much appreciated, thanks