Yealink T48G Won't Turn On (No Power)

[Bill.]

I was off for a couple of days and returned to my office, only to find that my Yealink T48G phone was completely off. I took the power adapter (YLPS052000B-US) and tried it on another T48G, and that phone powered up without problem. I then tried a switching power adapter from another T48G (even on a different known working power plug), but the phone still won't turn on at all.

Do you have any suggestions?

It is less than a year old. I contacted the seller and they say they only warranty for 90 days and I have to go through the manufacturer. I tried finding an RMA section from Yealink.com, but am unable to do so.