Hello and welcome.
If the fluid smells and looks burned, then something has failed internally. You could drop the pan and look for-and probably find alot of debre in the bottom of the pan and on the magnet.
There is nothing external to the trans. that can cause it to burn up. Since it was rebuit 5 months ago, it should still have a warranty. It is possible that the trans. cooler was not flushed during the rebuid, and some debre from the original failure got into the new trans. and cause premature were/failure.
Sorry to say, this trans. will need to come out of the car and get rebuilt or replaced.
If you are not very far over the mileage, good repair shop should help you out. A rebuilt trans should last at least as long as the original. If there were a valve or solenoid or somthing of that nature, it is too late since the fluid is bunred and it does not move. The damage has been done.
5 months and a few thousand over the warranty is now way to spend $1500. Contact the repair shop, and have them look at it.
Maybe i misunderstood. I thought you said afer it sites, it will go into gear, but only remporarily. The fluid being burned is the key. It is buned for a reason.
If perhaps you are mistaken, and the fluid is not actally burned- IE brown not red, then there could POSSIBLY be a problem in the valve body where valves are sticking. Would need a trans. shop to put a scanner on the computer and check solenoied and valve operation. Then they may remove the valvebody to check for sticking valves or debre. Removing the valve body is in the side of the trans. and the entire left side of the frame needs to be lowered to access it.
A trans. shop to do a diag. sheet is in order.