Replacement airpod

Hello,recently i lost my right airpod.One of my friend gave me his right airpod.when i was trying to connect it shown like another pair of airpods.Now i have 2 airpods pro in my settings..While i tried today to connect to listen ,just only the left one(the one with the case)And the right one nothing,bot of them we're connected.I tried resetting,and even resetting them i cannot...In info both show only the left airpod,but with another serial code.About resetting them...It's flashing white and after a bit of time green...