Issue with adding new users

Issue with adding new users

Hello,
 
I have an issue with adding new users to my account - I have purchased the Standard 10GB Edition plan which should allow me to add unlimited users. Right now I cannot add any new accounts at all as I always get an error message telling me that my user limit is reached and that I need to upgrade my plan. I have done that already and paid the $24 for it - what do I need to do next to finally make it work?
 
Thanks,
Katharina