Join Field Not Working

[LeviCecil]

I've been having this problem lately, where the join field tool won't work in Pro 2.6 or 2.7, or Python 3.7.9. I'll try to join on two fields that I know are identical, and it will say "WARNING 003237: Join had no matches." Is anyone else having this trouble? When I run the same script in Python 2.7, the fields join. This happens whether I'm trying to join a csv to a feature class, fc to fc, or a gdb table to fc. 

[Kalgul]

I spoke with Colorado State University's Geospatial Centroid, and they instantly found the issue.   I was trying to Join a Text(12) field with a Double field, which are incompatible.  The issue instantly went away when I created a new Text(12) field and applied the contents of the old Double field into the values with the Calculate Field utility, using a simple Arcade script. 

Text($feature.ID, '000000000000')

ID was the name of the old Double Field to pull from, and there are 12 zeroes to match the 12-digit text string.  There was a hitch at first, because I had an active selection.  Once I cleared that, the calculation went without a hitch, validation instantly worked with the Join function, and now it's Joined.

'WARNING 003237: Join had no matches.' is a completely inadequate error code.  ArcGIS Pro should 100% state "Warning, you are attempting to join incompatible field types.  Please ensure you are joining identical or compatible fields."