I think it would be a fairly clear cut debt case. It might take a bit of lawyering to collect on the debt, but there are firms which would take it on a contingency basis.
If they are trying to avoid payment it will kink any activity in the EU, all over a relatively paltry sum.
The lesson though is that if you're dealing with potential shysters, like NFT promoters and other dodgy stuff this firm is doing (who else pays 70k Euro per year plus commissions to telemarketers??) then make sure they have assets in your jurisdiction that you can put a lien on, and ideally require cash up front.
