ive been using the built in VPN now when i click on the VPN button im asked to setup the VPN

Have you done a [Restart] of Windows yet to ensure you have cleared most Windows settings and do you have more than one Profile? Has this happened after an update and have you enabled auto update Settings > About Firefox is so it may be a great idea to disable that. Have you found any relevant info when searching this forum that is related I suppose you have read the main guide https://support.mozilla.org/en-US/kb/built-in-vpn