There is a leak between the acrilic wall and the shower stall pan. Caulking using acrilic did not help. Shall I cut the plastic wall and/or use some special sealing material?

Thanks!

'm going to start my answer by stating that While I'm no expert in plastic or fiberglas repair I can give you my opinion of what I would do if faced with the same problem in my own home. And then I'm going to post this over in" Interior Home Improvement" where, hopefully, there are experts more knowledge then I.
For any kind of caulk or grout to work the surfaces must be prepared. The arera that you wish to caulk must be dry, clean and it helps if you can prime or lightly sand the surfaces. You may then apply Acrylic Caulk to the area. My bet is that the area you wished to caulk wasn't properly primed or prepared. But hey! What do I know? I'm just a plumber. Cheers, Tom