Section 107.71 Retesting after failure.
An applicant for a knowledge test who fails that test may not reapply for the test for 14 calendar days after failing the test.
My Commentary on Section 107.71 Retesting after failure.
So on top of this regulation forcing you to wait 14 days, you have to pay another $150 to take the test again.
FAA’s Discussion on Section 107.71 Retesting after failure from the Final Small Unmanned Aircraft Rule
The NPRM noted that some applicants may fail the initial aeronautical knowledge test the first time that they take it. To ensure that those applicants take the time to do additional studying and/or training (rather than simply take the test over and over again), the NPRM proposed to require that a person who fails the aeronautical knowledge test must wait 14 calendar days before retaking it. For the reasons discussed below, this rule will finalize this provision as proposed in the NPRM. 14 CFR 107.71.
One commenter suggested that an applicant who fails the knowledge test should be required to receive additional training in the area(s) of deficiency and receive an endorsement from a flight instructor in order to retake the test. The commenter rationalized that this would be consistent with current policy for pilot applicants with regards to failure and retesting, and will enhance safety by ensuring some level of oversight in the training process.
A person who fails the aeronautical knowledge test will receive a knowledge test report pointing out the areas of knowledge on which he or she did not test well. That person will then have 14 days to conduct additional study or training in those areas of knowledge prior to retaking the knowledge test. Specifying a prescriptive method of study is not necessary in this rule. Instead, the applicant will be incentivized to select the method of study that works best for him or her.