You didnt mention your Roku model # or firmware version (Settings/System/About) or app version (highlight the app and press Options (*) on the remote).
The Hulu app updated yesterday (8/18) to version 6.48.1 - this appears to be causing this issue on some devices.
Reinstall doesnt seem to fix it, but you can try regardless:
1) Remove the Hulu app (Highlight the app, press the Options (*) button on the remote, then Remove)
2) RESTART the Roku (Settings/System/System restart/Restart) <-- MUST DO THIS HERE!!!
3) Re-install the Hulu app
You need to contact Hulu about it: https://help.hulu.com/s/contactsupport