How are you watching? Are you using Hulu directly, or running Hulu through the Roku Channel? If through Roku Channel, it is yet another reason to NEVER subscribe through a 3rd party. Subscribe directly on the service's WEB SITE, then you have full control and usage on any supported device.
I'm not certain how using a service through Roku Channel works, but I assume they have some database that directs a selected show to a particular service. That database may not be correct. There were multiple posts about a show called "The Repair Shop" that Roku Channel said was available on Discovery+, but was actually no longer available.