Instagram Auto-Reply (keyword automation) never triggers on real DMs — either falls to fallback or gets zero response

This feature is in "beta" and I understand there may be bugs, but this looks like a significant one.

I've built an Instagram DM Auto-reply automation (Klaviyo's Social Auto-replies builder) and it will not trigger correctly on real Instagram messages, even though it's fully configured, saved, and shows as Live.

Setup:

• Trigger: Direct message containing keyword "SHOP" (also tested "access", "ECOMMERCE", "EC" — same result on all)
• Primary message: Collect email (Simple message type), using Klaviyo's built-in email-format validation
• Confirmation message: sends after a valid email reply, containing a discount code and shop link
• Instagram account is a business account, connected through our Meta Business Portfolio ("Shopify: fgyn34zy 1786465944 business"), which correctly manages our Empire Commerce Page/Instagram Profile

Bug — reproducible every time:
Sending the exact configured keyword from a real Instagram account produces one of two outcomes:

1. Accounts with prior conversation history with our business account get the generic "invalid response" fallback message, as if the keyword wasn't recognized — even typed exactly as configured.
2. Brand-new accounts with zero prior history get no response at all — not even a fallback — even after manually accepting the message out of Instagram's "Message Requests" folder into "General."

Troubleshooting already completed:

• Tested multiple distinct keywords (SHOP, access, ECOMMERCE, EC) — same failure every time
• Deleted the automation entirely and rebuilt it from scratch as a new automation ("Evergreen Campaign") — same failure persists
• Tested across three separate Instagram accounts: our own business account, a personal account with prior DM history, and a completely fresh account that had never messaged us before — same two failure modes as above
• Confirmed there's no minimum follower count required and the sender doesn't need to follow the account to receive a reply
• Confirmed there's no conversation routing set up to any other third-party app on the Instagram account
• Confirmed the correct Meta Business Portfolio is active and correctly linked to our Page/Instagram Profile
• Checked Instagram's personal "Apps and websites" authorization settings — nothing listed there
• Checked Meta Business Suite → Business Settings → Integrations → Connected apps for our Business Portfolio — only "Shopify by Facebook" is listed; no Klaviyo entry appears anywhere
• Clicked Klaviyo's own "Connected" status badge on the /social page — it doesn't open any menu, modal, or additional detail
• Confirmed messages are moved into Instagram's "General" inbox (out of Message Requests) before testing, with no change in behavior

Given the automation shows as connected and Live inside Klaviyo, but there's no visible Klaviyo entry anywhere in Meta's connected-apps list (personal or business side), this looks like it could be a permission/webhook sync issue between Klaviyo and Meta that isn't exposed in the standard settings screens.

I actually started this inquiry with Klaviyo support and they suggested I post it here, since live chat isn't available on our plan.

Has anyone else run into this, or found where this connection actually needs to be re-authorized/repaired? Happy to provide screenshots or more detail if it helps diagnose.