When running OpenCart 2.3.x.x on Servebolt you may stumble upon an issue where you are unable to add products to cart. This is because the session_id column in the _cart table is set to be type varchar (32) , meaning a maximum length of 32 characters. OpenCart is then unable to save the whole session ID.
You can fix this issue by altering the column type to e.g varchar (64)
