It was a pita to get mine in when I replaced the stock one. Try moving the filter around and see if it helps let it seat down in there fully. I got really frustrated but eventually was able to finagle it back into place.
I just did a new tank and pump and had the same issue. I needed to play with it to get the filter to sit down in the baffle just right to get it to fit.
Same issue here with a spectra premium tank. Had to finagle the pump a bit but eventually it did seat. IIRC I had to seat it with the filter sock slightly tilted up on the baffle
It was actually the 2 tabs under the top of the fuel pump holder ! They were bent out from me trying to force it down. Bent them back straight and it dropped in ! Thanks guys !