It looks like you're seeing that error message because you have a learntomod account created from one of the books. Accounts created from the books come with unlimited website access and 2-3 months access to the minecraft server.
We've added 2 more months of access to your account just now, but after that time runs out, and you'd still like to continue using learntomod, you can buy a recurring 1-yr learntomod subscription from learntomod.com. An access key will be emailed to the email you pay with. Then, just login as usual and click the account gear icon in the middle of the page -- scroll down and click the add time link -- then enter your access key,
If you buy the 1-yr subscription, you can opt out of automatic billing by emailing firstname.lastname@example.org