---
title: 4010: RCS capability check unavailable | API Docs
description: The RCS capability check could not run on the sender line.
---

The RCS capability check could not run on the sender line. This is an HTTP 503 error indicating a fault on the **sender** line, not a statement about the recipient.

## Troubleshooting

- Retry the request after 30 seconds.
- If it persists, send from a different line on your account and contact support.