I have a cert in Avalara CertCapture that I have changed to Exemption reason Taxable that is still exempting the customer in Avalara Avatax.
Currently you can not make a customer taxable by using the exemption reason taxable in Avalara CertCapture for Avalara Avatax.
It will thrown an error when trying to communicate with the admin console.
Instead simply add an invalid reason to the cert and update it.
You can do this in the Validation tab of the cert itself.