^^ hmmm.......I'm not sure about Passat, but on its brother vehicle, Golf mk7 which is built on the same MQB platform, the driver can always find-out what's causing Start Stop to not work.
Try this :
Press the Start Stop panel on the Vehicle status screen (sorry for the crappy picture):

You should then be presented with a list of things that are prohibiting SS operation like this:

Notice the human-head symbol on some of the entries - these are driver controlled reasons which can be manually changed (i.e by pressing a button). The entries that don't have this symbol are automatically determined by something else in the car which is beyond the driver's direct control
Don
Try this :
Press the Start Stop panel on the Vehicle status screen (sorry for the crappy picture):

You should then be presented with a list of things that are prohibiting SS operation like this:

Notice the human-head symbol on some of the entries - these are driver controlled reasons which can be manually changed (i.e by pressing a button). The entries that don't have this symbol are automatically determined by something else in the car which is beyond the driver's direct control
Don
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