I had a spare fob programmed for my 2020 Frontier SV, V-6, 2WD. It works as it should as does the original fob. However, now the yellow dashboard key warning light comes on every time the engine is running while using either fob. I changed the batteries on the fobs and left the truck battery disconnected for 4 hours. The dashboard key warning light is still on. Does anyone have any ideas on how to make it turn off. Thanks

Blinky green is a low battery, blinky yellow is a dead key or key outside the truck, solid yellow means there's a DTC somewhere in the I-key system. That can be almost anything in the system, BCM, IPDM, steering lock, etc, etc. You won't know what it is without getting a code-read.

The dashboard light is solid yellow. The original fob only has 3 buttons. The new spare one has 5 buttons. Could that be the problem ? Will getting a 3 button fob solve the problem ? Thanks

Yep, programming a fob with different buttons than the BCM expects will cause I-key system errors every time. There's no fix for it except to un-program the offending fob.