Radio remote control defective

Hello everyone, after a clutch repair in the workshop the radio remote control of my 406 2,2HDI FAP Break no longer works. I thought the thing is quite simple, they have the FZ-battery stuck off too long, and you only have to learn anew. It is in the operating instructions. Ignition OF Ignition A press immediately on the big button. Ignition switch off however not possible. Battery changed in the key also did nothing. The free workshop also tried it and was just as ni In order to check if the key is correct I have done the following: put into a TV short antenna. Keys held next to the TV, UHF, I think it was set to 433Mhz. Then you can see that the key after holding down the big button for a few seconds sends out some packet. So the key seems to be OK. Does anyone have an idea what else to do. Where is the ECU actually sitting at the 406 2.2HDI FAP Break?