My Jeep won’t start?

So I have a 2015 Jeep Grand Cherokee, I have
recently been having issues with it starting so when
I push the ignition switch everything comes on all of
my lights headlights brakes everything works when
I push the brake pedal and push the switch to start
the engine you can hear it click but it doesn’t
always turn over sometimes it’ll start sometimes it
won’t. I took A shop near base and I paid 400 for a
diagnostic and they said there was nothing wrong
with it I think they just took my money and told me
there was nothing wrong with it because I’m still
having the issue. The battery and the alternator
tested fine. When it doesn’t start I can hear the
starter clicking so the starter still works. Anybody
have any idea what’s going on