Did you receive an acknowledgement from the IRS on your first amended efile?
You want to ensure you have received acknowledgement of the first amendment before trying to amend the second one.
To complete the second amendment you will need to manipulate your return by deleting the Form 1040X, which will leave you with a 1040 "original" return that includes the changes from the first amended return.
Then, you will start the amend process over again to put in the information needed for the second amendment.
When you start the second amendment the balance or refund due should be $0.
How to Amend Your TurboTax Return a Second Time
