Speech has a source and a filter: the vocal folds in the larynx chop the airstream into a buzz, and the pitch of that buzz is set right there, below the mouth.
Above it the throat, mouth and lips form a tube whose resonances — the formants F1 and F2 — colour the buzz, and those two resonances are the vowel.
Tongue height mostly sets F1 (open mouth → high F1); backness and lip rounding set F2. So the classic vowel quadrilateral is quite literally a side-view map of where your tongue sits.
The buzz here never changes pitch — everything you hear is the filter.
Something in the simulation stopped unexpectedly — the lesson continues without it. You can move on; nothing you did was wrong.