This is a known issue that happens on many sites using Cloudflare. Please follow our SOCKS5 guide to reduce the occurrence of CAPTCHAs.
We support Windows 7 and newer, macOS X Yosemite (10.10) and newer, and Linux distributions such as Debian, Ubuntu, and Fedora running kernels 4.8.0 or newer. We also provide OpenVPN and WireGuard configuration files for any device that supports them.
Please make sure that you do not have any antivirus or third party firewalls that might be blocking / restricting access for installing the TAP Adapter correctly.
You can set the environment variable MULLVAD_LOCALE to the language you wish to use of the ones we have available:
If using Linux : MULLVAD_LOCALE=en-US ./mullvad-vpn
If using Windows you set it in: System -> Advanced system settings -> Environment Variables -> and then add a System variable called MULLVAD_LOCALE with the value of en-US for English.
If using macOS from a terminal: MULLVAD_LOCALE=en-US /Applications/Mullvad\ VPN.app/Contents/MacOS/Mullvad\ VPN
Keep in mind that you will need to restart the Mullvad VPN app for it to take effect.
This is an issue with the Windows TAP drivers, and it is seen more often when using torrents, what you can do is install the older TAP driver version 9.9.2_3 and see if that resolves the issue for you, remember to reconnect after installing it.
Make sure your running kernel and kernel headers are matching when you installed the WireGuard packages, If they do not, then upgrade them. Try rebooting and then see if it will load the kernel module correctly in a terminal by issuing sudo modprobe wireguard && lsmod | grep -i wireguard You might want to give installing and compiling the WireGuard source a try as occasionally packages for dists are not setting up things correctly.
This can happen if you set a MTU that is lower than 1280 in the WireGuard configuration file, make sure it is not set to lower than 1280 and then try again.