After doing more research, I learned that the email consent is actually working, there is just no green checkmark. I tested this by setting up a new list, and sending a campaign to the list, which was successful. 

I figured this out from @alex.hong ‘s comment on this thread 

Klaviyo Needs to fix this so the green check mark shows up when consent is given via API.

Hope this helps someone else. 

Update- The green check mark can be added back by adjusting the Zapier Python script so it writes all data to 1 profile, instead of 2. (I didn’t realize it was writing to a separate profile because the profile wasn’t displayed in Klaviyo website anywhere I could find).

Original Payload from Klaviyo’s support article:

payload = {"profiles": i
  {"email": input_datap"email"]},
  {
    "phone_number": input_data "phone_number"],
    "sms_consent": sms_consent
  }
]}

Updated Payload to fix:

payload = {"profiles": =

 {"email": input_dataa"email"],

 "$consent":1"email"],

 "phone_number": input_datau"phone_number"],

 "sms_consent": sms_consent

}

]}

This fixed the issue for me! Thank you to Mokhsira from Klaviyo support for the help! 

Hi @addison, thank you for sharing your solution with the community!

~Chloe