Is your debrief form currently set up to be descriptive text in the last question in your survey? If so and you do not need participants to submit a response to your debrief form, then there are a few workarounds you could try.
One good option would be to move your debrief form to an end of survey message, instead of making it a question/descriptive text within the survey itself. See more info on customizing end of survey messages here.
Another option would be to add a timer question to your survey. I am assuming the only thing on the last page of your survey is descriptive text with your debrief message. Simply add a new question to the very end of your survey, and change the question type to Timing (under the Advanced question type options). You can then set up the timer to auto-advance after a given number of seconds. Here's some more info on Timing questions.

If you don't have the Timing question option available for whatever reason, you could try adding Javascript to your debrief question that will auto-advance the page. TomG posted some cool Javascript that will do that in this community post. His code hides the 'previous' and 'next' buttons, but you can comment out the lines that hide those buttons if you'd still like them to be displayed, and the code should still work for you.