Add to cart stopped working after hosting move
We recently moved an older site built with webassist extensions to a different host. I thought everything was functioning OK, but the client just notified me the cart is no longer working. It appears clicking add to cart no longer adds items to the shopping cart. It's not just a redirect issue because going directly to the cart.php shows nothing in the cart.
I realize this is wide open question, but I'm just looking for some guidance on troubleshooting. It's likely an older version of eCart, as it was built in 2012 or so. What steps should I take to try and track down the issue?