If you’re having trouble calling your wife and her explanation is that she couldn’t hear and the miband didn’t vibrate, the solution to this is simple:
https://mi-store.pl/Porady-na-brak-przychodzacych-powiadomien-w-Mi-Band-blog-pol-1584445652.html
Sorry, but I couldn’t find as good a solution to the problem on English-language sites as the Polish distributor.