How can I reset the tests in the online GMAT prepration course so that I can take them again??

contact techsupport@manhattangmat.com

Please be aware that you can continue to take the tests as is - you are not required to reset anything in order to take more than 6 tests. The algorithm is allowed to give you questions you've seen before starting with test 7. But if you reset the tests, the algorithm will have no idea what you've seen before and so will still give you things you've seen anyway... resetting doesn't actually change the situation.