The first thing to do when your axolotl is sick is to check all of the water parameters. Specifically, what are the ammonia, nitrite, nitrate, and pH, and what temperature are you keeping the tank at? Report the values here, since those can be clues.
(If you don't have a water test kit, just assume that something is wrong with the tank parameters and do a large water change, like, 50-90%, using an appropriate dechlorinator. And then buy a test kit.)
If everything is fine with the water, consider any recent changes, such as new food, new water conditioner, new person around who may be feeding or doing water changes without you knowing.
Usually, fridging is for constipation, injuries, and to buy you time with a critically ill axolotl. It is stressful to change temperatures, so leave him in there until you have a better idea of what is wrong.
==> Have you read the fridging guide in the thread at the top of this forum? If not, do so. Pay particular attention to the temperature - most fridges are sett a few degrees too cold. Also, did you use fresh, dechlorinated water in the container that you have him in in the fridge? If the problem is in the tank water and you used that, the fridging isn't helping.
I hope your axolotl gets better.
