Welcome, @annakarenina!
We're grateful to have you here in the Roku Community.
Thanks for letting us know about this and we appreciate the troubleshooting steps you've done so far. Let's try to troubleshoot your affected Roku device further.
This is usually a signal or service issue. Have you tried rebooting your Roku streaming device to see if this helps? It's under Settings > System > Power (skip if unavailable) > System restart.
Keep us posted on how it goes and we'll go from there.
Best regards,
Carly
Carly Y.
Roku Community Moderator