Everything worked fine initially. Then we added a audio de-embedder for the Chromecast. So Chromecast into de-embedder, then hdmi out to Marantz. Shortly after that started having issues and eventually the hdmi Input quit working.

We would get a blue screen if any source was plugged I to that hdmi jack, if nothing connected we still see Marantz splash screen and can see Marantz UI.

Moved Chromecast via de embedder to hdmi 4, changed Input assign and was working great again. Used it for a could hours then suddenly quit working again.

Remove the de-embedder and didn't help. This time though, none of the rear inputs seem to work anymore. All show the blue screen if something is connected.

The hdmi jack on the front was leaving when I left last night but quit working at some point. I ONLY had the bluray connected via an HDbaseT extender feeding into Marantz then HDbaseT extender out to projector.

Is it possible that a device has too much voltage or something and could fry the hdmi inputs? Thinking the Chromecast or the $50 amazing audio de-embedder.

We did a full factory reset but didn't help. Not sure if there is a separate reset to reset the hdmi board. 

You'd think it might fry the audio extractor if the Chromecast "had too much voltage", as you put it. I tried one and it didn't maintain connection to the network, but haven't heard anything about blue screen with their Denon receiver. I didn't install an audio extractor, though.

Measure the DC voltage from the power supply for the Chromecast- it shouldn't be much higher than 5VDC, if it's regulated.

The only problems I have seen with HDMI were caused by cables.