Online Family Randomly blocks websites.

I have quite a few categories blocked on my child's computer.     One of the areas that I want them to use is the www.studyisland.com web site.   This site I have specifically added to there permitted list in the configuration.   

 

When they first log into the site they are able to connect and it works fine.   Then after spending 45 minutes using the site and taking the tests as desired.  Norton suddenly decides that it is a blocked site and doesn't let her save her progress.   This is very frustrating.     I have it installed on 2 different computers and both running windows 7.    

 

In all cases it will allow a site to be contacted the first time but then later it will just suddenly change it's mind.  

 

The randomness of the functionality makes the software useless   the only way I can have my child complete an assignment in the study web site is to turn off the blocking   and the whole reason why I have the blocking is because she gets distracted from her work by the other web sites that I am trying to block.      

 

Any suggestions on how to make this thing work.