Seems to have come right on its own. Vodacom heard my pleas
EDIT:
I see I am able to check the router's balance using my primary phone'e login profile, but when I login using the router's (newly created) profile the problem exists. Can I delete the router's profile from my main profile somewhere as I don't really need it any more?
EDIT2:
I now also see that I seem to have 2 main profiles. One I login with my cellphone number and another I login with my email address. The 2 profiles have different passwords. When I login with my 'email address' profile I get this locked in loop problem, the same as when I login with my WiFi router profile. The other profile works fine. Weird.