On bootup I no longer have my progress and it just gives me the option to start a new game.
Anyone experienced this or know how to fix, I saw some suggestions for the steam version where the cloud backups were at, but nothing for the GOG version.

OK, I figured out my issue.
In case anyone else runs into this same issue I'm going to post my solution.
For some reason Mad Max was saving to the OneDrive folder on my machine, even though I had OneDrive disabled and wasn't logged in to an account in OneDrive.
I was able to copy the files out of OneDrive\Documents\WB Games\Mad Max\Saves
and paste them to somewhere temporary.
Uninstall OneDrive.
Restart my machine.
Then copy the files from the temporary location to C:\Users\{UserName}\Documents\WB Games\Mad Max\Saves
(might be C:\Users\{UserName}\OneDrive\Documents\WB Games\Mad Max\Saves depending on your machine I think)

After doing that and starting up Mad Max my saves had been restored.

thanks for the information

Hey, this comment does have anything to do with the topic, I would like to ask you about something involving Mad Max and how its files are, If you would help me out it really should only take a few messages, I just want to know how the dlc is handled as gog lists all of them.