I now found that CBSubs have upgraded to 3.0 and 2.x will discontinue the service.
I have purchased CBSubs with "Maximum number of Users: 5000" 2 month ago.
When I tried to install 3.0, I was required to upgrade the plan with an additional cost.
I haven't even installed the one I purchased to my live site.
Should I really pay more on upgrading this? I am not sure why so even my maintenance period still remain for almost 10 months...