This series uses An iGPU (Intel Iris 5100), as you are getting power so either the logic board has a failure or the CPU/iGPU has failed.
You’ll need to open the system up and make a detailed inspection of the logic board looking for damaged components. Follow this guide [guide|33077] and review Steps 10 ~ 12 in this [guide|30410] to help you identify the major components. If you see something suspect take a tight picture as well as one to help identify when it is on the logic board posting it here so we can see it.