classalpha

hi everyone

my A class is having some issue with the remote Key. Hope someone could help me out here.
The key was not able to unlock or lock the car or start the car. I had to use the physical key to unlock,
and insert the Key into the ignition to start the car.
Thinking it was just the key battery, i replace both my keys with new battery. and i tested it was 2.99V on the new battery.

now here's the weird part.
i was able to lock the car with the new battery Key. But when i press the lock or unlock button again, it didn't respond.
although i could still start the car with key in ignition.
So i manually lock the car and walk away while pressing the lock button on the remote key.
suddenly i heard the car locking horn and the car was lock with the key.

i could lock or unlock the car with remote only after a few minutes between each press.
and i could only start the car with the manual key turn on the ignition. As the car indicated on the display 'no key found'

i had been searching the web and this forum and couldn't find a solution. tried many re-syn method still doesn't help.

thanks in advance to helping