2008 nini cooper base- std trans! Evu replaced as it was showing ignition miss on cyl # 1I installed the ecu and the part under the dash pad! These parts came with a compatible key fob- there is no communication between the fob and system/it looks like the battery in the fob is dead! It is a completely sealed fob! What can I do at this point?

 

Did you try putting the fob into the holder for a bit to try charging it? Those internal batteries don't hold a charge forever and are recharged while you're driving along.