Thank you and thanks to all who have tried to help me! I'll keep you updated.
Thank you. I just have had time to sit and reset the APN. it still does not connect. I have excellent signal strength but no internet connection.
Now that you have reset the APN and have IPv4/IPv6 showing, are you able to get any other devices (laptop, husband's phone, etc) to connect to your hotspot. [Now have to verify your hotspot is actually working].
If you can verify that your hotspot is working, try performing a Network Connection Reset from within Roku. (Settings/System/Advanced System Settings/Network Connection Reset, Reset Connection).
Also, restart your phone and perform a Connection Reset there as well. (Settings/More/Network Settings Reset)
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If still can't connect, try using the 2.4ghz band of the hotspot. (Settings/Mobile Hotspot and Tethering/Mobile Hotspot Settings/Setup Mobile Hotspot/[select 2.4ghz band for AP band] )
If still having issues, try configuring the hotspot to use IPv4-only rather than IPv4/IPv6. ( Some of the TMobile hotspots have issues resolving the IP protocols when both are enabled, and others are fine. Kind of device specific.)
It appears that there is a problem with how your Onn Roku TV connects to your phone's hotspot. Here are some measures you can take to try to remedy the problem:
Check that your phone's hotspot is activated and that your TV is connecting to the correct network name and password. You may check this in your TV's network settings.
Restart both your phone and your television. This frequently resolves connection troubles.
Try resetting your TV's network settings to the factory defaults. Go to Settings > System > Advanced system settings > Network connection reset > Reset connection to accomplish this.
Check to see if your TV has any software upgrades available. Go to Settings > System > System update > Check now to do so.
If none of these measures work, you may need to contact Onn or Roku support for additional assistance.
Thank you. I'll try this. Yes, my hotspot connects to my fire stick and kindle without issues, but on the fire stick, it connects to all streaming apps except YouTube.