I've my Domains hosted in Trap17. My Account is suspended due to lack of enough points, but I was able to use the Google Apps for Domains for checking out my mail. But recently I'm not able to send or receive any mail, I think the problem is in the MX Record which I've set in trap17 cPanel.

When I access my domain http://laschatz.info/ I get the Account suspended page which is the usual page, but I'm not getting that page when I access my Addon Domains xatre.info, it is pointing to ComputingHostst name servers.

Is there anything I need to do to make my addon domains work?

Unless you modified CNAME for your domain to Google Apps, your cpanel handles all MX traffic. Which means, if your hosting account is suspended you cannot receive any email.

I cannot even see your add-on domain probably due to disconnection from your main hosting account. The only way to resolve this issue is to bring your main hosting account to current (unsuspend) and then re-add your add-on domain.