Alice55
The Roku device (and any other wireless/wifi device) uses the password that you have assigned for the SSID (network names) in your router.
In a router, there are different bands. (usually 2.4ghz and 5ghz bands). Each band has a SSID name and password. (network name and password). Most people use the same password for all the bands. If you are using different passwords for the different bands, then this is likely your issue.
You may be using 'password A' for connecting to the 2.4ghz band, and using 'password B' for the 5ghz band. If you connect your Roku to the 2.4ghz band, then you will need to use password A. If you connect your Roku to your 5ghz band, you will need to use password B. This likely explains why you are needing to use different passwords (new and original).
Try going into your router and changing all the SSID bands/names to use the same password and your Roku should be able to connect to whatever band you are using. (and be able to use the same password as your computer). Again, depending on the exact model number of your Netgear router, you may find that you have one 2.4ghz band and multiple 5ghz bands you can connect to, as well as additional Guest networks depending on how you set up your router and network.
Additionally, make sure you are not confusing the router's password (admin portal) with the router's wifi password.