Unable to install Norton Online Backup

About a year ago I quit Norton 360 and online backup because they created problems on my computer. I told them to cancel my backup completely.

 

I have returned to using Norton but this time I am using only Norton Internet Security.

 

I went online and purchased Online Backup,  I piad 49.95 for it.  Then I downloaded it successfully.  Then I clicked it to install and got a message saying I cannot do it a new computer.  Hey, this is not a new computer.  It is the same as what I used.

 

It also said that I already used up 21 of 25 GB.

 

Why is Norton so difficult to work with?  I am tempted to quit it again - for good. 

 

What gives?

 

Thanks.