Is there in fact no water getting into the machine when the fault occurs?

External valves? You mean the faucets to which the hoses connect? If you disconnect the water supply hoses from the washer, run them into a bucket and get a full flow of water, then the faucets are OK and the problem is at the machine itself.

There should be debris screens inside the water valves on the machine, where the hoses connect. A no-fill situation can arise if the screens are badly clogged.

Thank you for the quick response!

There is water getting into the machine. You can plainly see that through the front-loading 'window'. When we put it on hot water vs. cold water, there seems to be more water flow on the hot and less water flow when we put it on cold.

Yes by external valves I mean the where the hoses connect to the water supply. They were old so we decided to replace them, hoping it might solve the problem.

We checked the debris screens and they are clean.

It's weird. I'll turn the wash on and it seems to be working fine then when I go to check on it there's an NF error when it goes through the rinse cycle. I press start again and it continues through the cycle and seems to fill up fine.

Any other recommendations? I hope I've described the problem well enough, let me know if you have any other things I can trouble shoot.

Thank You!

It's still doing it! After it goes through the 1st lit rinse cycle it gives us the nF error but then I press Start and it starts spinning around and you can tell there's tons of water in there because it sloshes all around. Any suggestions?

Just an idea ... Do you have flood-check water hoses or whatever those things are called? Typically, braided hoses with a integral gizmo that stops the flow in case of a leak? Those hoses can cause trouble with machines that purposely moderate the flow-rate to control the temperature mix. The machine moderates or pulses the water valve to control the water flow for mixing to a target temperature, the hose gizmo senses the low flow rate as a leak and triggers to shut off the water. The machine reads that as a fill fault.

Try unplugging machine waiting a few minutes and plug machine back in. My machine started right up again with no issues.