"Easy to see" is different than easy to understand. Those familiar with AVR setups, especially Denton/Marantz, will not have much difficulty in a basic setup and configuration using the onscreen GUI, web setup or even the front display. Assume new posters know nothing about a particular AVR, its GUI, web setup and speaker configuration setup and advise accordingly. They need to reset the thing and read the manual from cover to cover. Fortunately, manuals can now be downloaded and specific settings can be word searched and gone to immediately while one has the web setup up and running at the same time. Posters do well to put up pics of settings, components and cables when asking for help with a problem. Otherwise, there is no way to know if what they post is in agreement with what is actually configured and connected.
I did assume the OP doesn't know these AVRs well- that's the reason I included instructions on how to find the IP address and about using the gui, which is far easier than trying to wade through the menu using the AVR's display. It's easy enough to use the On Screen Display setting so it can be seen using a TV, but it's better to be able to see tabs and navigate through the menu without needing to click on the 'Back' button and accidentally leaving the setup menu, which isn't hard to do.
As long as the config isn't saved to the AVR and it hasn't been reset, messing around in the gui can't hurt anything and it will make learning easier than reading the manual which I know is something that most people won't do because that's like being punished for buying something.
However, reading about how to do something isn't best for all people, so there's YouTube and by searching for 'Denon AVR-3301CI setup', I found a lot of useful information with graphics from a TV shown.
I can't see doing a hard reset until after finding out how it's set up- that would undo anything that may work as it is, requiring the OP to learn to use the menu to make it work at all.
I would start with YouTube videos since they can be a quicker way than reading the manual.
I have a Denon AVR in my basement but I don't remember if it can be set up with the gui- if it can, I think I'll make a video since I haven't seen any for that on YouTube. It has some video issues, but I know the network card is OK since I use the Denon app and AirPlay with that one.