I think this one is not a clear cut case but I think you should have a strong case for denied boarding scenario. You had a ticket airline hasn’t cancelled the flight but they refused you to fly.
Would be good to know where did you purchased your ticket as this could become some sort of consumer law issues which is outside of EU reg.
hopefully others will able to provide you more useful info but probably I would have done the same.
I would also check if travel insurance would cover this as it can be an easier way to reclaim your money.