I have to jump start my 2007 accent after I drive to work and let it sit all day. Only happens when temps hit high 80's. Had battery checked out and it had no problems.

Take the battery to a auto parts store and have it tested. If a cell has failed it won't charge up no matter how long it sits on a charger

sounds like you have a failing ecu. the capacitors in the ecu are worn out. there has been a lot of problems with the ecu on mazda's over the years, only take one out put overload from the alternator and the ecu starts playing up. no codes come up as it don't code its self. having the battery off is like a reset.

when you try to start engine does the starter motor engage or do you hear a clicking ? also when you turn on ignition do you hear a click ?

If the battery is actually good and does not have a ( bad cell ) then I would be looking at a bad ground wire.

I would say it's a bad temp sending unit.

must be the ignition coil damage. need to check the coil is operate or not. check spark.

I just experienced the issue: clic-clac-nothing. Jumps start: same clic-clac-nothing. I set the 4th gear and moved the car. Just started like day one!
It's good, so far but I don't know why...

You need to remove the battery cables and clean the connections with a wire battery terminal cleaning tool. Then start the car and check the voltage at the battery with a multimeter. It should be between 13.5-16 volts. Any less and the alternator is defective. If this all checks out and you are 100% sure nothing is on drawing power then the battery more than likely has a dead cell. Remove the battery and take it to your parts store and have it tested. You will probably need a new battery.

it sounds like you need to replace your battery.jumping it to get it started will charge the battery especially if you are driving it around and will hold charge for a bit.but if truck is sitting all night then battery is just draining

The low voltage accessory battery and high voltage hybrid drive battery are in the trunk area. If hit from behind the hybrid battery may have been damaged. The high voltage battery is the one that actually starts the car. This battery is too high voltage for a normal person to check. Call the dealer so they can get in the shop to fix with the right kind safety procedures.