Re-saving PSDs with Maximize Compatibility

I've been using Ps for decades. Before Lightroom existed, best practice was to turn "maximize compatibility" off to save space unless you needed compatibility with specific DTP programs. When Lightroom came along, best practice changed to turning "maximize compatibility" on. That left users like me with many files that couldn't be imported into Lightroom. Logic would suggest that simply re-saving these files after the "maximize compatibility" option was changed in Preferences would be enough to solve the problem. It is not. What do I have to do to get Ps to resave the files so they can be imported into Lr?

FWIW, I have tried re-sizing (w/o resampling) and saving. That didn't work. I've tried adding an empty layer. That didn't work. This process shouldn't be this hard. I'm looking for a fast, non-destructive way to do this without adding unnecessary size to the file. (I understand that maximizing compatibility necessarily increases file size. I'm talking about anything else.)