There have been some rough spots with the Western South rollout of LAANC. Of course, no one is issuing explanations. The effort is no doubt a huge task, but it's apparent that communication with the commercial pilot community was not on their original checklist. Someone should fix that unfortunate oversight.
Is VGT an FAA tower? Have you checked the ARCGIS grid in that airspace?
If so, is your altitude request appropriate? If these answers are affirmative, they might simply be having a hiccup. Keep trying! And good luck!