@Xico.Mocte15-_ 

A Solid yellow light indicates the Deco is in Start up Mode.  If its not changing then that indicates the unit may have an issue.  Since the Hard Reset did not work the only recourse is to get the unit replaced.  To do that we would need to first have you register the product on our warranty portal  https://myproducts.tp-link.com/.  If the serial number does not register you will want to use the serial number on the box.  If you don't have the box look at the serial on both units, it should be the same except for 1 character.  Change this character to an X for the group serial.  

After the product is registered you will need to upload a proof of purchase for us to review.  We need to ensure the product came from an official authorized retailer.  If not there is a chance we can't replace and you would need to contact the seller. 

Lastly we need to verify there were no disquailfers like adding a 3rd party software, Physical damage, Acts of nature- including power outages.  

If that all checks out we can authorize a RMA and get that unit replaced.