Chromecast allows the user to cast with, or without, an internet connection.
All you need for a Chromecast to work is a wifi (network) connection. You do not need internet. Internet access will allow you to cast online content via the Chromecast to a connected device/TV. Without internet, you can still cast local file storage (files on your computer or local media server) via the Chromecast over your wifi (network) to the connected device/TV.
Therefore, you are merely casting to the Chromecast (that is connected via HDMI) to your RokuTV. The RokuTV does not even have to be connected to your network in this scenario because the Chromecast is delivering its content via the HDMI connection.
EDIT-- after re-reading your post, not sure if you mean a Chromecast device (above info then applies), or if you mean the Cast feature from within Chrome on a laptop (if so, then it is via wifi/network connection). Regardless, the internet does not figure into it in these scenarios on the RokuTV side of things. During casting, the RokuTV does not have to be connected to the internet to "receive" the casted content. Just has to be connected to the same wifi (network) if the latter scenario.
ETA: When everything was working properly, I didn't need the chromecast to watch the bedroom TV, I could stream all the channels I wanted to from abc news to youtube. Now I can only cast to the one tv. The other one is now an ornament on the wall
Unfortunately, until you make that setting change for the IPType (IPv4 or IPv4v6), the streaming devices are likely going to have issues connecting and streaming from the internet.
Your previous T9 was likely configured in this manner. Newer ones have reportedly been set to IPv6 at time of issue or existing ones have been changed by firmware updates. There are a few postings in this community regarding this behavior.
https://community.roku.com/t5/Wi-Fi-connectivity/Error-code-009-no-internet-connection/td-p/829899
https://community.roku.com/t5/Wi-Fi-connectivity/Roku-not-connecting-to-T-Mobile-hotspot/td-p/786737
Thank you. I wound up going back and getting another T9 and it didn't work either. So I asked for the original one and they were able to pinpoint which one it was. I hooked it back up and everything is working perfectly, so, it WAS the devices, not my setup, Thanks for spending so much of your time on my question.
Happy New Year, and be well
