Internet connection is fine but ROKU won't connect.

I posting this because while I think I found the answer here, I wanted to verify with 'the experts':-)
Also, I'm posting this for my sisters, who are 1100 miles away. My sister and her husband recently got a ROKU for my other sister because they cancelled her cable TV service and are going to full streaming per my suggestion.

Anyway, once she had internet service set up, they set up the ROKU with no problems. However, Comcast office screwed up and shut off her internet service a week later. She's getting that free internet becasue she's disabled and on a very low fixed income....

SO my older sister and her husband were there today to reset everything and she does indeed have internet service but she can't watch anything using the ROKU (and that's all she'll have). They tried a factory reset and that didn't work, although, I'm not sure if they did it right (I"m not there).

Also, they said they got an error code but can't recall the code:-(.....

So I'm thinking that it a setting on my sisters Xfinity app on her phone. She was told that she had to have the app for them to start the service.

They won't be able to go there to do that for her until tomorrow. So just in case, is there anything else they can check?

Thanks in advance.