Negative feedback from the teacher
And in this case, there are two options for solving the problem: you can ask the supervisor to talk with the teacher or go to the dean's office on your own and talk to the reviewer personally.
If the supervisor closely followed the progress of writing and compiling a scientific work, then he will also not be very pleased to receive a negative assessment for his work. And you can ask the supervisor to convince the reviewer to put at least a "three", it will be enough for admission.
If you decide to go to the dean's office in person, then when talking with the dean and the reviewer, you should be confident. It is important to provide reasons, arguments why you should be given a normal grade and allowed to defend your thesis.
The work did not pass anti-plagiarism
There should be no plagiarism in scientific work, which means that writing it should be done independently, and not just copied everything from the Internet. And if plagiarism is found in the thesis, then they can even be expelled for this without the right to recovery.
If a student deliberately cheated via Free Essay Writers and was caught doing it, then big problems can await him. But you can try to fix everything, it is important to immediately contact the dean's office, talk with the dean, give reasons for your justification. In the best case, protection can be carried over to the next year.
But sometimes a technical error can occur in the program that is used to check for plagiarism. And if the student is confident in the uniqueness of his work, then he can demand a second check through the dean's office.