You are calculating tax for a customer that has an exemption certificate on file in AvaTax or CertCapture. However tax is calculating, when it didn't used to.
With the AvaTax for Quickbooks release version .79 the customer job information is no longer used in the customer code.
If you have exemption certificates that were active before you updated to v.79, you will need to update the customer code to remove the job information.
If you use ECMS, you will need to revoke and copy the original certificate. Making sure to remove the job information from the customer code.