From this thread
I have the same problem. The tooltip says in red: to RE I would need Armormech 440, The thing is, I have 450, it just doesn't seem to register it.
Another, even bigger bug is, that some item says I need Armormech 440 (this is in white so accepts my level 450), but I also need ADVANCED SYNTHWEAVING !?!??
Sounds like the same issue.