My car won't start. I have had several boost with susses over the last few weeks. Today after a boost it did not turn on and the battery is tested and good. what is the problem?

Measure the voltage across the car battery with a volt meter with the alternator running .. It needs to read 13.4 volts or higher to charge the battery.

Why didn't the mechanic continue on & resolve the issue?

You don't have the experience to do so, as your here

No one can tell you what is wrong without the vehicle to test,
common sense

Can't be boosting today's car or bad things happen

Dead batteries have to be disconnected & charged

Now you will pay several hundred to diagnose those issues

Very likely bad battery. Most places that sell them will install for free.

Sounds like the clutch disc is toast.
Its possible the throw-out bearing has failed, but either way the transmission has to come out to fix either part.

Check all fuses ,wiring anywhere short or check alternatour

just had the same problem and i ended up having to change the altenator, for 2 or 3 weeks i would have to bang on the altenator with a hammer while it was running because my battery light would keep coming on. but after a few taps with a hammer you could actually here it start working again. i did that one to many times and broke the housing on the altenator and eventually had to replace it.

If it is a 3.8 engine change the crank sensor,they go bad on the 3.8 engines.

have battery and relays tested --leaning toward battery fault

check your battery terminal very well and re tight very well