First make sure you have all the wiring properly connected to the battery.
Many times because some manufacturers use , black wire for positive and white wire for ground things get messed up.
Were the slides and levelers an issue before you started , replacing battery and converter?
Follow the power + wire from the battery post , somewhere in the first 3' of the
wire you should find a fuse or circuit breaker , because of the high draw of the levelers and slide mechanism these items are not usually fused on the main board.
My last 5er, the 12v circuit breakers ( one for the main fuse board and a second for the level legs ) were mounted just through the battery compartment wall away from fumes that would cause corrosion. They were VERY hard to see.