i didn't receive any response to the web form i submitted 17 days ago.
any suggestions on how i should proceed?
I do not understand your question, since I gave you the answer already on June 1.
The chances are 99% that OS wont answer that request at all or invoke the "extraordinary circumstances" clause (which is most likely not true).
Best advise would be to delegate the claim to a specialized EC261/2004 collection agency, which focuses on enforcing claims in Austria - once OS has refused the money.