What should I do if I cannot accept any of the hypotheses in a replicated experiment?
Honestly report about the results you have achieved, including any errors and omissions in the method that have occurred, or any reasons why you think the results are not as expected. 

If you produce a good analysis and report, then it won't matter so much that the results were not as expected. 

The point of a bachelor thesis is mainly to demonstrate that the student is capable of applying the skills learned over the prior years in a larger setting. The goal is not to produce original publishable results.