Welcome to GoY hope you find the site helpful.
I have had similar problems in the past.
Sometimes it works better if damp other times dry.
try 1.
Find a stick that will go in the drainage hole at the bottom and push up from that end.
if that doesn't work
try 2. using a bread knife type blade saw away at the roots from the top of the pot so it is a square set of cuts. loosing some roots wont do any major harm. then push up from the bottom.

hope this helps.

SBG - your use of breadknives always amuses me. Do you have a stock of them or just the one trusty old one?

I have 2, a coarser one and a fine one. Shoved into very hot soapy water after use then back in the drawer. Both were bought when I was a student in 1977, so very old now and still work brilliantly.

I wonder if the technique worked. Would love to know.