Welcome to AA, starlifter2, and happy to see another Richmonder on board!
Otocinclus cats are relatively delicate, and it is not uncommon for them to die soon after purchase. They are often starved unintentionally at the
LFS because they don't generally have algae in those aquariums, and I understand that they lose some of the enzymes or healthy bacteria perhaps in their guts and it makes them unable to digest food once they get to your tank.
What I like to do is when the
LFS gets some in I wait and get mine after they have been there for at least a week, because the
LFS loses them routinely as well. The ones that survive a week are generally more hardy, and then they do better at home. Be sure you have something for them to eat, like diatoms (brown algae) or feed them algae wafers.
Where did you get them? You might be able to get a store credit.