What is wrong with the word "fascinatingly"

When I add it into my vocabulary it changes to “FASCINATINGLY” And then it sounds like abbreviation ! When I change it to another word - it works correctly.

Nothing…it would usually be worded differently but it’s a fine word i think. Instead of ‘it’s fascinatingly simple’ i think it would more often be worded ‘its simplicity is fascinating’. Can’t explain why grammatically because i don’t know !