Hopefully that'll fix it...looked it up ..it's called the adblue metering valve. So hopefully it is blocked with calcified adblue and a clean out fixes the issue.Car is in at my long time garage, fingers crossed it’s the problem as discussed above. I’ll let you know how I get on.
That's gas I had something similar ... Although in the main I think it has a separate battery or more of a storage capacity device for stop start. I think the nox sensors in general are a prob with these ... I got a software update before my adblue issue...so I wouldn't be surprised if I get a nox issue again, Mercedes website states they should replace your sensors when they do the update IF necessary...the IF being key word.... but I think the job I had done and you just had done, clearing out the calcified adblue from the metering valve, will sort your adblue issueCuriously my stop start has started working again. Perhaps that was a software issue and not a drained battery through lack of use during lockdown as I suspected.
Be interested if this happens again. I had a software update, then got an adblue warning, with engine warning light. On holiday in Wales, had to pay for a fix. On the way back from Wales - same problem, and going in to my local MB dealer for another fix. Annoying. Sure it is an MB software/hardware issue...Car is in at my long time garage, fingers crossed it’s the problem as discussed above. I’ll let you know how I get on.