Nagoya UT72 problem

I recently installed 50w transceiver in my vehicle and temporarily have it hooked into a Nagoya UT72 mag mount.

This evening I was waiting in my vehicle to check into net and realized I wasn’t getting signal. I stepped out of the car and was able to rx on my $25 uv5r.

I’m VERY new to amateur radio and also now very confused as to why I can’t get reception on an antenna that costs twice as much baofeng with stock antenna. I’ve seen mention damaging the coax, however, this is not the problem as mine is carefully routed without pinch points. I’ve also read about grounding but I would imagine that’s not a problem and my radio is grounding to my negative battery terminal.

I’ve tried to research this problem but don’t know exactly what to search for. I have no formal radio training beyond the hamstudy.org app and was just recently licensed this week.

Any help is much appreciated.