Pebble Steel battery replaced

Hello, hoping someone can advise me here (and sorry if this is an obvious answer to some).

I purchased a sealed Pebble Steel off of eBay the other week, it stated the battery was dead, so I ordered this battery-

https://www.mpfproducts.com/120mah-p121112-p150116-battery-for-pebble-steel-e-paper-smartwatch/

Installed it fine, seemed good to go. I put it on yesterday morning for the first time, maybe 7am, and by 3pm it was dead.

I had read somewhere, for a different Pebble, someone suggested completely draining the new battery and then charging it fully, so that’s that I did last night.

I put the watch on this morning, 7am, and it’s now 11:30am and it’s almost completely dead.

I assume there is either some serious Bluetooth issue that is causing this, or the battery is a dud. When we order batteries, like the above, are they new? I mean I know it is sealed, but has it been sitting around for 10+ years in a factory somewhere or are they still being manufactured?

Just not sure if I should buy another battery or if the issue lies somewhere else. I guess I can try charging the watch and wearing it tomorrow in airplane mode, that would cross off it being a BT issue if it’s still dying quickly.

I’m on an iPhone 15 Pro Max, iOS 18.3 if it matters.