https://www.rokucom-support.com/hulu-not-working-on-roku-quick-fix/ When your Hulu app is not working on the Roku streaming device, that means there is some troublesome with the Hulu app. To remove this, all you need to do is easily read this full set. When you have the issues with Roku, the strongest explanation is doing a soft reset. If things do not fix the situation, a factory hard reset will do the thing. Here’s how you can do both.
1. Soft Reset Roku:

Doing a soft reset will restart the Roku without losing settings or data. This is your first thing when Hulu is not working on Roku.

From remote:

You may try resetting using your remote control if the Roku is frozen by holding the following buttons:

Home 5 times
Up 1 time
Rewind 2 times
Fast Forward 2 times
This should work on all Roku models.

(For Models Like Roku 4, Premier and Ultra)

· Select Settings>System>Power>System Restart. Do it from home screen. Using Button (Older Models)

· Search for the reset button on the back or bottom of the device. Some models will call for a paper clip for pushing the button. Reset button in Roku 2, press a button and release after a second. Device will reset successfully. – Power Pull

· If the above stuff doesn’t interest you, you should disconnect the power cord for about 20 seconds and then plug it back in. You should contact 1-800-961-7126 for the more step of the power cord connection