Everything's been working great for months, but after updating to InDesign 16.3.2 recently, I started getting the error message attached and am not sure why. It's also functioning fine in my other Adobe apps.
"Could not start FontExplorer X Pro because it could not be found or the license file is missing"
FEX 7.2.6 (build 20687)
InDesign plugin 3.5.6
macOS 10.15.7 (19H1323)
I'm not entirely sure if it's an InDesign or FEX issue, but have reported the issue to Monotype as well.