693 - Amount must be greater than or equal to zero. Usage: At least one other status code is required to identify which amount element is in error.

It appears that you sent out a zero charge claim and this payer does not accept zero charge claims.

Why did Therabill allow me to submit a zero charge claim?

Some payers allow zero charge claims (for reporting purposes) and others do not.   Therabill does not know which payers do allow this and which ones do not.  However, when you create the claim in Therabill, a warning will be presented to you if one of your claims has a zero charge.

How do I fix this?

You need to edit the service code charge amount on the edit session form in Therabill.  Change the 0.00 charge to have a charge amount that is greater than zero.  Remember to save your session.  Once you have done that, you can then resubmit this charge from the EDI rejection page.