I'm completely lost. My shower has minimal hot water pressure, colds fine. I changed out the cartridge and the hot water TK is brand new and recently checked by a plumber. Cannot find any reason why I am not getting pressure. All other taps are fine. Any ideas?

Is it a single handle? Remove the cartridge and open the side tap. Make sure the line is open. Many times the orifice gets plugged and it is fairly small. Also check to see if any flex line is bent.

The cartridge is brand new, so nothing should be plugged. There are no side ports in them either.

It is a single handle valve and the lines are copper so nothing should be bent. Do you have any other suggestions, appreciate your help.