I recently purchased ExpressVPN and having been trying to set up openvpn on my router.
I’ve downloaded the ovpn file from Expressvpn but every time I try to upload it to my router I get “file format or path invalid”.
Any help would be appreciated!
I'd try another browser. I used the ExpressVPN instructions (link) for manual router setup on an AC86U and it worked just fine with the ovpn file provided. The basic process for me was: download ovpn file and upload it to the router, copy over login and password, and copy over the extra configuration they provide into the text area on the bottom of the VPN client config screen.
It might also be worth a try to move the OVPN file to the root of the drive to avoid any possible issues with the path. Also if the browser displayed the ovpn file instead of downloading it directly, try downloading it with right-click->save as... so you get the original file. Saving something the browser already displays will usually screw up the format.