Color Settings File not available in Acrobat

I just checked a WIn 10 & 11 system, and yes, I see the same thing.

However, I did a search on this and, from another thread, it seems to be an issue with Protected Mode disallowing the ability to select a custom setting. If you go to Acrobat > Preferences > Security [Enhanced] and turn off Enable Protected Mode, (restart Acrobat), custom .csf should then appear in the Color Mangement settings and will also report your Synchronized status. This, of course, defeats the benefit of Protected Mode, so tread carefully. I'm guessing their thinking is, since a custom .csf could possibly be crafted into a malicious agent, Protected Mode is preventing all but the ones part of the default installation from loading. Someone else may know more on this and chime in, but that's my best answer to you right now. Apparently, Protected Mode used to be shipped OFF by default in previous versions of Acrobat, but lately it ships ON by default, which might explain a change in behaviour in your situation. (btw, this same setting in Mac Acrobat does not cause this issue).