I have never had much success with the pill popper; and I never have luck with liquid formulas either. This is just meant to sympathize, been there, done that!

Here is the best solution I have:

I sit in the recliner with the cat in my lap. Wedge the cat in between me and the armrest. The cat's butt is up against the back of the chair so she can't squirm out that way.

Wrap my left arm (I am right handed) around the cat, hold front paws down, squeeze cat in to me.

Using right hand, holding pill, squeeze jaw open just in front of the joint, and push pill down cat's throat.

Hold cat, pet her, offer a treat to "wash it down," basically trying to convince the cat this was "fun" so she will leave with a happy feeling for the next time.

In between pills, sit with the cat like this in the chair peroidically so she never knows when it is pill time. And stroke, offer treats, try to get her purring, so it is a fun thing.

Best wishes. It is not fun, not easy.