Mercedes Benz S Class electric windows don't work

The car is parked garaged most of the year in Botswana. I live and work in India so only get to drive it 2ce a year for about 10 days. Recently the battery ran flat - the main battery in the engine bay. This was replaced with a genuine mercedes battery. I however noticed that the electric windows no longer work both rear and front passenger sides. Only the drivers side works. This fault persists when using the central consol buttons and the individual door buttons.
Checked all the fuses in the entire car (unlike other cars where the diagram is on the fuse cover this vehicles does not have this). Fuse compartment in engine, under the steering and between the armrest in rear seat. All fuses intact
Took the car to a local Bosch certified dealer to check. They ran a computer diagnostic which was not helpful in detecting the fault. It may have not been genuine mercedes software. They also checked all the fuses and relays. All OK.
They then put the car into sleep mode for 24 hours by disconnecting both batteries and rebooting up the next day. The fault still persists. Only drivers window operational.
Everything else is perfectly fine car runs and drives wonderfully.
They recommend I take it to a Mercedes dealership for software upgrade. Unfortunately I am unable to do that as the nearest dealership is over 900km away in South Africa, and I have since returned to work in India.
Can't sleep well at night knowing my pride and joy is not 100%.
Can you please advise on what what the problem may be and if anyone else has experienced this.
Regards