My daughter took two Covid tests on the same day, each returned with different results

My 19 year-old daughter came to Guyana from America for Christmas. Before she came, she had received two Moderna vaccines and a COVID test. After spending one week in Guyana, she took the COVID test at one of the government authorized COVID testing sites. She tested positive for COVID. I didn’t believe the results so on the same day I took her to a different government authorized COVID testing site, and she tested negative for COVID. My daughter didn’t show any symptoms of COVID. Editor, can someone from the Ministry of Health explain to me why one test was positive and one negative? What if she didn’t take the second test, she would have been stuck in Guyana, miss two weeks of university and had to pay for new plane tickets. Who would have compensated her for missing her flights and school? Would the government, or the COVID testing center, compensate? I want answers for my questions.