If network becomes unavailable after you enable AdGuard protection, try doing the following:
If you have DNS protection enabled, switch to a different DNS server and/or protocol in Protection (second icon from the left in the bottom row) → DNS protection → DNS server.
If the previous advice didn’t help, try disabling DNS protection completely.
Go to Settings (right-most icon in the bottom row) → General → Advanced → Low-level settings and enable Restore VPN automatically.