I can open the trunk with the remote, from the inside latch, and using the trunk switch as long as I got the key near the trunk. But if all the door are unlocked and the key is inside the car I can’t open the trunk using the trunk switch. I replaced the battery for the remote. Not sure if this is normal or I need to buy brand name batteries.

 

Normal. The key needs to be on you when you press the trunk lid as it only detects it up to a few feet whether the car is locked or unlocked.