Here comes Mr. Solution!
Solution:
/testfor @e[type=Item_Frame] {TileX:-510,TileY:77,TileZ:-201,Item:{id:"minecraft:tripwire_hook",tag:{display:{Name:"Key2A"}}}}
Errors:
- If you will do a testfor or a scoreboard command with tags you always have to write in formal way (Ex: {id:stone} = {id:"minecraft:stone"} | {Count:1} = {Count:1b} , etc.)
Tips:
- You can just write <item_frame> instead of <Item_Frame> (No Caps)
- If there's nothing else with the name <Key2A> you can just write {tag:{display:{Name:"Key2A"}}} with no {id:"minecraft:trpwire_hook"}
Hope it works