Hi Mitchell,
can you tell us what version of the Windows OS is installed on the server side?
To access any desktop via NoMachine you need a system account on that computer. You can use the local username assigned to your account on the Windows machine. To check the local username, just go into your C: drive, select Users and check what your local username is. Are you sure you are using the right password? If there is Win 11 on that machine, don’t use the PIN that Windows 11 asks you when unlocking the screen.
Some more tips about acceptable usernames and formats are available in the knowledge base article here:
https://kb.nomachine.com/AR03S01118
If that doesn’t help, please send us logs from the both sides. You can do this by following the instructions here: https://kb.nomachine.com/DT07S00243. You can zip them up and send to forum[at]nomachine[dot]com.