Hello,
Sorry to hear this!
So that I can try to investigate your issue further, would you mind sending across your Two Point Museum folder? To do so follow this navigation path in file explorer: C:\Users\<username>\AppData\LocalLow\Two Point Studios\Two Point Museum. Once located, "Zip" the folder up (right click and you should see the option).
Zipping a folder is a way of compressing it into a smaller size. If you don't have an option to do this, you may need to download a program to help. I use one called 7zip which can be obtained here. The top option - ".exe - 64bit windows..." should do the trick. Once zipped up, you can attach it to your reply.
If you would like to try and repair your save, there are steps to do so here. Please make sure to back up your files before you do!
Thanks,
Chizel
At some point, my campaign file has become corrupted: when I tried to resume the game, all 'campaign' progress was lost, but yet when I open Momento Mile (the only available museum), the museum itself was at the 8 year stage, corresponding to where I left it in the campaign.