When this issue occurs, some users have reported success by Factory Resetting the problem device (in your case, the RokuTV), and activating/setting up using a new account (new email address).
By doing the above, it will affect any premium subscriptions you have so a couple of options here.
I haven't seen if any users tried the following, but if you find creating a new account for your RokuTV fixes your issue, you could then Factory Reset again, and try to once again setup under the old account. If that does not work (ie. original issue returns), then cancel your subscriptions, setup the RokuTV under the new account, and resubscribe to your subscriptions under this new account. (for some subscriptions, you may just be able to use the subscription login credentials on this new Roku account and be good to go.)
Feel free to update and post back if still having issues.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102