I agree this a tough call especially if you have a good relation with the entity, however I also look at it this way (not just for the TA but in general), they were very very quick to take your money, but when it comes to returning the service they are not playing ball. You should have no worries in trying to obtain what is rightfully yours. There are may other TA's around. This crisis has shown a lot of true colours of entities which had it relatively easy and could do a little bit of what they wanted and played Sheriff.

Of course it could well be that the TA is waiting for the funds from the airline, so maybe worth getting into contact with the TA one last time and if you do not get a satisfactory response, I would file the claim.