Even though I've stated in the package properties that there should be a maximun of 20 email accounts, when I try to add an email account to one of the accounts in the package, it says "Sorry, you have exceeded the maximum allowed email accounts." I only have 1 package, and this is the only account in that package. Any ideas what the problem could be?

I don't see such problem with your main account.
Please send en email to support@hostony.com with detailed explanation of your problem including account's domain name and steps to reproduce the problem.