The only way to test is to remove all VPN apps, delete the profile(s) and reset network settings. Please this path to delete VPN profiles,
iphone > Settings > General > scroll down > VPN & Device Management > delete all profiles. Then reset network settings.
Reset your network settings
If you're using iOS or iPadOS 15 or later, tap Settings > General > Transfer or Reset [Device] > Reset > Reset Network Settings.
If you're using iOS or iPadOS 14 or earlier, tap Settings > General > Reset > Reset Network Settings.
This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before.
If your iPhone or iPad won't connect to a Wi-Fi network - Apple Support