Also, try different battery brands. I once had the oddest experience: Duracell Coppertops would *****not**** power up either of two Nikon MD-12 motor drives, while Everyready Energizers would power the MD-12's just fine. The difference as I could ascertain at that time ('86 or '87) was that the brand that worked had a very tiny little bump, almost nipple-like, on the positive contacts, which made a set of two batteries end-to-end just a tiny bit longer overall. The MD-12 took four sets of two, which layed in a horizontal orientation in the battery chamber. I had ALWAYS bought Energizers, but there was a big sale on Coppertops, so I bought a large supply of them on sale, took them home, and loaded up all three of my cameras with them...and the two MD-12 units would NOT function, but the Nikon F3's MD-4 DID work with them!! This was a perplexing and memorable scenario.
I noticed subsequent to that,over a couple of decades, that "some" Asian-market manufactured batteries had this tiny,tiny little nipple on them, while most domestic USA-market batteries were a totally flat on their positive contacts.