Update here; Received an email from Twilio support on this and just incase anyone was wondering:
"Services like Google Voice, Facebook, and Skype, which use short codes (e.g. 55555) to send SMS will not be able to send messages to Twilio phone numbers. This is because short code carriers have arrangements to exchange messages with mobile phone numbers only, and Twilio phone numbers are not considered mobile numbers. Unfortunately, we can not guarantee delivery from these incoming messages."
@craigleblanc Thanks for the heads up and bummer Twilio isn't going to work for this use case! You know what, I remember listening to an Asian Efficiency (AE) podcast and I think they ran into a similar issue with 2-step access. Their solution was to use a Grasshopper number. While Grasshopper isn't a supported app on Zapier, I would imagine you could get SMS notifications to your email and then use a Zap to trigger off of the message and send that information to Slack. Is that something you'd be up for trying?
You've probably sorted this now but... if an authenticator app is an option, we use 1password to store One Time Passwords so the whole team can access them, rather than using a phone number. (Bitwarden does this too but requires a mobile app to scan the onscreen QR code).
Hi @craigleblanc! I was wondering if you had an update on this? Were you able to find a way to make your verification flow work using SMS by Zapier or 1password?