Also, if anyone is interested, apparently this is the correct battery for the keys. I bought a different one on amazon and the little pieces on the battery are not in the correct orientation so you must modify it. With the new battery, I followed the normal reprogramming and now the doors open via remote no problem.

Rechargeable Battery for BMW Remote Key 2pcs-in Alarm Systems & Security from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group