A tomentosa has heart shaped leaves like the rest of Aristolochia....and I have transferred PV cats back and forth from several species of PV without trouble....and they have eaten readily. I believe mine came bareroot with small plants growing.... Take a look at your leaves, and then google it and look at some pics and see if it's the same.

I've known of cats not switching hosts in cases where they are larger and the hosts are more varied.....but I've never seen this with PV cats. Now, it may take them a few hours to adjust.....so leave the tomentosa in a way they can get to it, and give them a day or so (without taking away the fimbriata) and see what they do?

My cats go between a. tomentosa, a. serpentaria, and a. clematitis readily. Cats don't like old, tough leaves, so if that's all the a. tomentosa has, they won't eat it for that reason.
Another possibility is that you were sent a tropical aristolochia - they're easier to come by, so the seller may have, inadvertently or knowingly, sent that to you.
A. tomentosa doesn't grow from a bulb, just the normal roots. It will colonize in time, but that takes quite a few years.
MissSherry

I bought a tropical before I knew anything about the differences in pipevine, it was trilobata, and they won't have anything to do with that. But these are still very young, so I don't think the leaves would be too tough, they are heart shaped, not tri lobed like the trilobata. Well, maybe they're just spoiled, and only want the fimbriata which they have already eated to a nub.

I think Kahakitag may be right that they are spoiled.
I have gold-rim cats (not PVS) that came with the A. triloba plant I bought. They have eaten it to the nubs and I don't have a way to get more triloba so I offered fimbriata. The smaller cats took to it but the larger ones wouldn't switch.
Now the fimbriata is down to nothing and I'm trying to get them to switch to A. tomentosa and nothing doing.
That's all I've got left. They either eat the tomentosa or starve. I don't have anything else.
I predict when there is nothing else they'll eat it.

Mine eat A. tomentosa, A. fimbriata, and A. durior with no problems! I switch their diet of the Aristolochia salad while they're young...I figure it is like they are children and you need to have them 'eat their mixed veggies' now or they won't want to eat them later! tee-hee!

Well, now I'm beginning to think that these tomentosas were sprayed with chemicals because I had two little cats that nibbled some of the leaves, and now they are both dying. I feel so bad, but since I bought them from mail order natives off Ebay, which someone on this forum suggested, I thought for sure they would be caterpillar friendly. I bought up all the fimbriata that I could find locally (one nursery had it) even though it was all eated down to a nub, and just hoping that it will leaf back out in time for some more cats. I've got probably 20 plants in pots all around my yard. I've raised BST cats this year, and they aren't nearly as voracious eaters as PVS, I wasn't quite prepared for it.