Apple TV 4th gen Remote not working

My Apple TV, 4th Generation bought last year, does not pair anymore with my Siri Remote. I tried following methods without success:

• Reset Apple TV

• Unplugging Apple TV for six seconds and retry

• Pressing Menu and +

• Pressing Menu and -

• Charing remote for more than 1hour

After pressing Menu and + the apple TV box lamp does blink for each remote press but it does not react. Strangely, it does only react to the Menu and TV icon pressed simultaneously which forces to restart the Apple TV. Since I don't have the iOS App configured, I can also not enter the pairing code. I researched a lot and can not find any solutions. Can some please help me?

Thanks