I’m working on a typeface with 2 masters, when I try to export a variable version it gives me this error:
“These glyphs are not compatible: fehDotless-ar.medi, heh-ar.medi.ss01, hehDoachashmee-ar.fina, hehDoachashmee-ar.medi, allah-ar
Probably the TrueType conversion failed”
I exported both otf and ttf formats successfully, and all glyphs look compatible.
I also activated Enforce Compatibility Check parameter but no change.
I’m using Glyphs 3.0.4
Can you post a screenshot of the paths of one of the glyphs? I assume there is something that cannot be converted into OTVAR curves. E.g. an outside overlap, a stroke, or a mask.
Can you please try the latest cutting edge version? (You can activate cutting edge versions in Preferences > Updates)
Newest version is 3.0.5. You have to go to preferences and check cutting edge versions to be able to update to that, like GeorgSeifert said 
Can you send me the .glyphs file?
Sent
You somehow added intermediate coordinates to the Bold master:
Use this script in the macro window to remove it (with the problematic layer active):
del(Layer.attributes["coordinates"])
Thank you, indeed that was the problem.
I’m having the same issue but I’m using intermediate layers + cap components.
Are cap components + special layers supported?
Cap components can produce incompatible outlines in some circumstances. Can you send me the file that I can have a look?
Sent!
I found the problem and fixed it.