Unfazed
Sorry you missed my point. You believe correctly... but LARS/FIS is the lowest priority and if the controller is getting calls from other aircraft (maybe on other frequencies... it is not unknown to be monitoring 3-4 freqs at a time) that are a higher priority, you may not receive an immemdiate answer to your call, I suspect (hope)the Controller wasn't totally ignoring you, but was waiting for pause when (s)he could get back to you... i.e. that's the excuse.
Mind you, the unit might have told you on your initial call it was working to capacity, so if possible and all you required was FIS you might switch to another unit... or expect problems? That's inexcusable!