Duo with Vue.js and C#, verifying 2FA response


So far I have been able to get signed requests returned to the Duo iframe from my C# back end. Because I am using Vue and this particular app is a SPA, I have been trying to verify the 2FA response but with no success. Just using the ‘post_action’ argument is not enough because I need to run a callback after the response from the server. I tried playing with the ‘submit_callback’ but the documentation is vague at best. Anyone else have any success?