If your aam panna is thick while making it, you may have used less or more pulp. Add water while making it; if you add water later to make it less thick, it may ruin the taste.
After it is ready, it will have a sticky, semi-liquid texture. When stored in the fridge, it will get thick. Don’t worry, take it out of the fridge and let it rest at room temperature, and it should come back to standard thickness in some time.
If you want to speed up the process of bringing the aam panna to room temperature, then take the jar where you have stored it and rinse it in regular or lukewarm water. Ensure the jar is entirely closed and water can not enter it.