Did you install a Microsoft Windows 10 upgrade or update and have a problem with MaxIm ?
It's easy to fix.

I noticed this again wtih Windows 10 1903. (If you check the Windows About)

Sometimes MaxIm's file associations for .FIT files or other formats may be temporarily reset or broken by Windows updates.
Windows may try to fix this when you double click a FITS file. This usually works, and you will see the MaxIm installer window briefly.

If it doesn't automatically fix this after a Windows 10 upgrade / update, just do the following:
Start... Windows Settings (the gear)... Apps.
Find MaxIm DL in the list of programs.
Click it, and select Modify.
When the installer comes up, select Repair.
That's it - you are back in business.

No need to uninstall.

Note that other programs may have this problem as well.
For example, DC3 Dreams ACP Expert is also affected, and it will auto-repair itself.

If you need help with MaxIm, please visit the Diffraction Limited forum:

(I'm an ACP customer and I work for Diffraction Limited)