so I don't use wireless much on my roku. I do when we take it with us traveling.
normally it makes me use my phone to log into the roku and set up the wifi and password.
is that what you are doing or is there some new onscreen thing that lets you setup wifi for yours?

is the new one also not able to see your router?
do you know if you have 5 ghz or 2.4 ghz?

for your old devices, have you tried to forget your wifi connection and do a search again?
or you could load an app on your phone to sniff wifi connections.

if your old devices still remember the wifi and say you lost the broadcast ssd, they would still connect.
the roku might be stupid and not able to find it because it isn't broadcasting the ssd.
There may be a setting to connect even if you don't see the ssd. but I am not sure on a roku.

lastly, you might check your wifi settings to ensure it is broadcasting the ssd, and that the name is still correct.