A Bosch Performance 1200 Washer-Dryer had the child-proof lock enabled. The key icon was flashing and all controls were disabled – they just caused a beep-beep no-go sound.
You need to select the mode that was locked (for instance drying…), then hold down the pause button for five seconds. That will then unlock the child-lock. It does not work if you select, via the dial, a mode other than the one previously locked. This explains why so many people have trouble as they usually will have selected the mode that they want to use rather than the one that was last used. Bosch really ought to clarify this better in all their user manuals!
By the way, not all the manuals could be downloaded and you need the exact & complete model number from inside the door. For instance Model Number WVD24560FF/06 could not be downloaded from Bosch – an error response is all you get.