4th gen-Channel in guide, strong signal, won’t play

Hi there! I have a channel 18.1 (bounce) and it’s sub channels that show strong signals when doing a rescan. They appear in the guide but won’t play. Getting channel_not_found

I’ve rebooted the modem, Tablo and Roku. Any ideas? I’m a newbie. BTW, these channels are great when running directly to the tv with a direct connection from the antenna (no Tablo)

Using a Roku express. Thanks!