So I configured Gmail to handle our domain's emails. But the problem is last week, January 25 it expired causing our mails to bounce back.
We already renewed it today and saw the site back online but we're still unable to send/receive email using our domain name.
Do you think I need to re-setup Gmail / Google Apps?
With you only renewing it today, it's likely that the DNS records for it haven't propagated fully. I'm assuming by not being able to send mail you mean that any mails you do send aren't reaching their destination - this will happen if the remote mailserver can't find any MX records for your domain.
It's probably a good idea to check anyway and make sure that your domain has MX records set up - just in case anything's changed due to the domain lapsing.
