Ugh....ugh..ugh.. should've read this part of the guide multiple times!

"Caution: There is a tiny metal contact under the circuit board that makes contact with the battery. Unstick the circuit board gently to avoid damaging this contact."

The metal contact ended up breaking off. :/

You live and you learn! Hopefully someone else learns from my mistake!

Thanks for the heads up. I just checked the batteries I got from Ebay and Indeed got sent Z55 instead of Z55H ( even though the listing said I was buying Z55H batteries.