Protection turns back off when I turn it on
This happens because for some reason AdGuard is unable to establish a local VPN profile. Try doing the following:
Check for system updates. Sometimes there are system bugs that prevent apps from establishing a local VPN profile, and it’s important to always have the latest updates installed.
Sometimes problems with establishing a local VPN can be caused by using a profile with a Restricted Mode. If you have such a profile, you can learn how to grant AdGuard necessary permissions or how to switch to an unrestricted account from this Knowledge base article.
There are known cases when the manufacturer deliberately disables the option to create local VPNs. Check that your device model allows that.