Double Opt-In not receiving opt-in email

We've set up an Oauth integration and all seems to be working well except one detail - users who sign up on double opt-in aren't receiving their opt-in emails. I've tested with a demo brand I've set up but haven't received the email for any recent signups when having double opt-in selected, and so the users are stuck in a "never subscribed" state. If using single opt-in, the user is subscribed to email marketing correctly.

Some more details:
- We first create a profile, then hit the subscribe profiles endpoint to opt them into email marketing

- We're using the klaviyo-api node package

- The oauth app has these permissions: events:read events:write profiles:read profiles:write lists:read lists:write subscriptions:read subscriptions:write