My keyless entry does not work anymore - 1995 Buick Regal

Sounds like the contacts in the buttons are not making contact.. you may want to try taking the remote apart and cleaning the contacts and seeing what happens. If the remote is truely dead you may need a new remote

they are all easy fixes with skills and tools.
in this case a $10 voltmeter
when you do all that is battery voltage at 12.6v?
and all fuses good
and engine runs perfectly for over 1 minute?
and the idiot lamps are all happy, running,
CEL not glowing running?????????????

Is this an issue with all 2008 HHR remotes??? Highly doubtful , probably the vehicles keyless entry system . Taking the vehicle to a qualified repair shop an having the keyless entry system checked for DTC'S - diagnostic trouble code's . Do you know what a DTC is ?
The keyless entry system is a vehicle entry device. The keyless entry system is used in conjunction with the body control module (BCM) to remotely activate certain vehicle features. Keyless entry will lock/unlock the doors, or release the rear compartment lid when a corresponding button on the keyless entry transmitter is pressed. This is accomplished by the transmitter sending a radio frequency to the remote control door lock receiver (RCDLR). The RCDLR interprets the signal and activates the requested function via a serial data message to the BCM. A low transmitter or vehicle battery or radio frequency (RF) interference from aftermarket devices, such as 2-way radios, power inverters, computers, etc., may cause a system malfunction. High RF traffic areas may also cause interference that could lead to a malfunction. Keyless entry allows you to operate the following components:
• Door locks
• Liftgate lock
• Remote rear doors (Panel only)
• Vehicle locator/panic alarm
• Illuminated entry lamps
• Remote vehicle start
The keyless entry system has the following components:
• Keyless entry transmitters
• Keyless entry antenna
• 2 Way Advanced Remote Start RCDLR
• BCM

Guessing will not fix this .

2007 Impala remote starter will not work and I must be next to the car for the keyless entry to work. I have changed tha batteries in both remotes

Before replacing any Relay. Try disconnecting the negative side of the battery for at least 2-minutes to de-energize the security system, re-setting itself. The reconnect the battery and try your security (and options) system again.
The only other big question that you will have to know: is this a factory installed security system or an aftermarket security system? This makes a difference in security systems, relays etc.

check the fuses in the truck. there is one that works the keyless entry sensor

The keyless entry is designed to work with the doors closed (closed - not locked). If the door ajar sensor thinks the door is open the keyless entry is disabled. When you manually lock the door it might tighten the door just enough to activate the keyless entry. I would try slamming all the doors closed and then see if the keyless entry works. If it still wont work have the wiring checked on the front door lock.

the keyless entry system is tied into the computer system and needs to reprogramed by the dealership

Make sure you have inserted battery correctly in key. If it doesn't work on one side, flip it on the other. Should work..

my keyless entry has been working great we went on vacation. it quit working i cheched the fuses and the battery in the remote everything is fine just does not work anymore