FireFox 91.0.1, extensions "Hoxx VPN" and "SetupVPN" seems not to work anymore

System : Linux Mint 20.2 FireFox : 91.0.1 (64-bit) Plugins/extensions "Hoxx VPN" and "SetupVPN" seems not to work anymore This is since FireFox 91.0.1 It takes a long time (about 30sec) connecting to the VPN, with no result. (no connection) Both say something like : ''Result <country> (SERVERS) 3.11.4 In some cases VPN extensions are not enough to bypass the firewall in your network. Extensions have only limited permissions on your computer and have limited capabilities. We highly recommend to download our desktop client. It uses a very sophisticated VPN software and can bypass most of the firewalls. '' Regards, Rob