Key Takeaways
- Two-way failures are usually SIM slot, default SMS app, notification access, or a phone that slept — not a missing OpenAPI field.
- Replies arrive at the MSISDN that sent. Dual SIM confusion is the classic “inbox is empty” bug.
- Keep OTP off promotional two-way lines so STOP bots cannot eat authentication threads.
- Webhook handlers need signatures and idempotency. Duplicate agent replies are an ownership bug.
- You bring the Android and operator credit. Inbound does not include airtime. Platform pricing is devices plus send volume.
android sms gateway two way sms troubleshooting starts on the radio, not in your CRM mapping. Pillar: two-way SMS inbox. This spoke is empty inbox, duplicate replies, and STOP colliding with OTP — not a rewrite of that page.
Live fields: Developer Center. Setup: device setup. You bring phones and operator credit. Devices and send volume.
Reply · toward the sending SIM
If they texted the other slot, your inbox is honestly empty.
Inbound path in one paragraph
Customer texts your MSISDN → operator delivers to that SIM → Android receives → app forwards to the control plane / webhook. Break any hop and the UI looks dead. Gateway model, webhooks.
An agent answering in three tools is not “rich two-way.” It is three receipts for one STOP.
Symptom table
| Symptom | Likely cause | Check | Fix |
|---|---|---|---|
| Native Messages has it, inbox does not | Grants / default SMS app | SMS + notification access | Permissions |
| Empty everywhere | Wrong MSISDN / slot | Which SIM sent outbound | Slot map after reboot |
| Gaps overnight | OEM sleep | Exemptions | Uptime |
| Double replies | Agent + auto-reply | Who owns the thread | STOP / auto-reply |
Default SMS app and grants
Some OEMs only deliver reliably to the default SMS app. Notification access is a separate toggle. Notification access. Retest after OS update. Real handsets.
Do not auto-reply into OTP
Promo STOP on the auth SIM trains filters and confuses users. OTP. Messaging practices. SMS Retriever on the customer app is unrelated (Retriever).
Webhook vs inbox UI
UI empty but webhook 200s: you are looking at the wrong console. Webhook silent: signatures, TLS, retries. DLR is outbound status, not inbound body. Dual SIM: multi-device.
Next steps
Staff reply to the production MSISDN, watch native Messages then the inbox, then the webhook. Install the app. Spend 300 lifetime SMS only as the outbound half of that drill.
Related product pages
Jump to the live product docs for this topic—not another long-form article.
- two-way SMS inboxReplies on your SIM
- SMS auto-reply and STOP keywordsOpt-out and keywords
- SMS API documentationLive endpoint reference
- device and SMS volume pricingPlans and allowances
