Three beautiful donuts. Like hidden object pictures, where one must search what has changed.
This problem will be solved by moving to the front time of the relevant part of the lecture.
In addition, you can check various information by searching with the search function at the top right of the ba.
It has been mentioned several times in connection with this issue (same issue)
Don’t focus on the instructor’s explanation, but focus on the screen
I put it on snap just like he said I put it on face project just like he said I hid the faces just like he said.
Ask the author, perhaps he’ll have a suggestion:
The Solidify modifier has the direction in which the Face protrudes.
If you check with the wire frame view, you can see if the issue is related to this. 
It would be faster to use the search function at the top right than to ask questions and get answers.
If you want to get answers to your questions, you need to explain your problems better.