When I try to forward an attachment to a colleague, I get a "Reached your limit" message.

I am trying to forward a submission to another user using the email tool.  When i click "send," an error message comes up stating "Ooops...reached your limits!"

How can I remove this and re-enable the forward and reply features on my account?

You are trying to send your form in email correct? There are limits set for forwarding the form / submissions. For free account the limit is 2 forwards per hour.

These limits are higher for paid users and if you need higher limits you should upgrade your account. You can wait for a while before trying again and it should work for you just fine.