The rubber response pads wore down and made it unresponsive. So I threw on a used Duncan response pad to get it to return.
I have heard looping yoyos require a different string type. Cotton I believe? Is the string really that important? I have been using polyester I think.
I always use Poly string when I loop. Is it possible that the string is getting caught between the bearing and the side of the yoyo? This can shred string really fast.
I normally use 50/50 type 8 string on my loopers. Cotton seems to work better for me in some cases, particularly on fixed axle, but it wears much quicker than other types.
That sounds like the issue, try some small bearing yyf pads and see if it helps.
EDIT: Also, since you mentioned the yo-yo is old i’d recommend you check the bearing. If the bearing is locked up or has any rust it can wear out strings faster too.