If you cannot make protonVPN work it is caused by some system incompatibility or a system not properly updated.
ProtonVPN is installed using AUR and AUR is unsupported using Manjaro as well as Arch.
The issue may be caused as AUR buildscripts expects Arch package level - which is NOT possible using Manjaro stable branch.
pacman-mirrors -G
If you get stable then uninstall protonvpn
sudo pacman -Rns protonvpn
And switch to unstable and run a full system sync.
sudo pacman-mirrors -aS unstable && sudo pacman -Syyu
Then build protonvpn
pamac build protonvpn
Finally you can connect using the command line
$ protonvpn-cli c nl-free#142056
Setting up Proton VPN.
Connecting to Proton VPN on NL-FREE#142056 with UDP.
Successfully connected to Proton VPN.
Or you can launch the GUI from your system’s app launcher panel
