Roku Player refusing to connect to WiFi Connection

[vortalexfan]

Greetings, my parents bought a couple of years ago a Roku Player for their TV (which is an older flat-panel TV that came without Smart TV Software Built-in) and the Roku worked fine at their old house but as soon as they moved into their new house last year the Roku suddenly started developing WiFi connection issues, such as continuous buffering during videos and giving connection error messages when attempting to connect it to the WiFi connection in their home.
They do have Comcast/Xfinity High Speed Internet at their home with a modem that doubles as a dual-channel Wireless Router, if that helps any, with figuring things out.

I'm kind of at a loss at what might be going on with their Roku, because my Roku isn't having any connection issues and is still going strong yet, and I have the same kind of internet as my parents have at their house...

Any ideas as to what the trouble might be?