One of our mini Cooper (r56) keys (that you slot in the dash & press the starter) which charge wirelessly whilst in use had died but was included with the car when we bought it.

Not knowing what / why wherefore of the key unit beyond it being rammed expensive to replace / get fixed at a "pants down" mini / bmw garage I found a company on eBay which diagnosed / repaired & cleaner up the key in a days turnaround for 20 (other brands too but likely more).

Smarts are often not the only car in a family, but prone to wear & year too! ...the seller is recommended by myself for a good & cheap fix (potential) ..If in the same boat.