Thank you for your patience. We have resolved the issue with the a recent update to Microsoft Excel which creates XLSX files which can't be imported into JMP on Windows.
JMP 13.2.1 is now available. Install this maintenance release for all software improvements of JMP 13.2 and a fix for Problem Note 60946, which affects users of Microsoft Office on Windows.
Enhancements and bug fixes for JMP 13 and JMP Pro 13 are available now in maintenance release 13.2.1. Please go to jmp.com/update today to update your software—at no charge.
Keep your software updated by setting the software preferences to automatically check for updates—in JMP, go to File>Preferences>JMP Updates, and then select the “Check for Updates” box.
So maybe this update is not as minor as I thought. I have 2 addins on the file exchange that no longer work correctly on this version. Is there a way for me to remove them from the file exchange until I diagnose what's going on?
... on the otherhand it looks like I just happened to discover the problems at the same time as I did the update. Correlation != cause & effect!