There are a few possible reasons why your customers are reaching a page that says you are under maintenance. Don't worry. Both can be fixed very easily.
The first reason is that you forgot to take yourself off of maintenance when you were updating your site. Simply go to the MY ACCOUNT tab under the OPTIONS button and click Maintenance to OFF then click SAVE. This will return your site to a live state again.
The second is that you are a new subscriber and you have not filled in all the Company Details. To complete this task, go to the MY ACCOUNT tab under the OPTIONS button and fill in the Phone #, Company Name, Company Address, and Company Website. Then click SAVE. After you hit SAVE, go back and click OFF to Maintenance so you turn your site to a live state. We use this information to build your site and your emails and this information is required for Can Spam compliance. That is why you are under Maintenance until the task is complete.
The third reason is that you have used all your credits for the month, you will automatically be placed under Maintenance. To check this, go to the MY ACCOUNT tab under the OPTIONS button, and see if you have a message that tells you you are our of credits. If you are, CONGRATULATIONS, that means that lots of customers are sharing your offer. To add more credits you can upgrade to a higher plan OR you can wait until next billing month begins and you will get a new batch of credits. The choice is yours!