Carl-
The only time I have had the same symptoms as you with my Dolphin is when the water temp was really low or when the bag was super full.

Your temp is not the problem. Does it still refuse to climb when you first put it in with a clean bag?If so, then something is wrong.

Double check that you have it set to climb walls in the menu.....you probably already have done that, but I would set it to not climb, then reset it to climb just in case.

Hope it works out for you.