Why did I fail a drug test for benzos, if I only take flexeril, mobic, (meloxicam) alieve, vitamins, and Azo cranberry?

Drug tests. Drug tests for benzodiazeprines can be positive if you are taking it. Some of benzodiazeprines are xanax, (alprazolam) librium, klonopin, clorazepate, valium), ativan, restoril, Halcion .... Some other medications can cause a false positive result in benzodiazepine urine tests. These drugs can be tolectin, aleve, etodolac, daypro, zoloft ...
Unclear. There is not just one urine drug screen for benzos. There are multiple benzos and each has its own screen. You would need to find out the exact test and what other substances can cause a positive test. It would most likely be one of the vitamins you took, as the others don't typically cause problems.