The error message "SSL handshake invalid chain" typically suggests that there's an issue with your SSL certificate chain. A certificate chain is a sequence of certificates, where each certificate in the chain is signed by the subsequent certificate, leading up to a trusted root certificate. If any part of this chain is missing or incorrect, it could lead to this error.

Here are some steps to debug and possibly fix this issue:

1. **Check Your SSL Certificate:** Verify that your SSL certificate is correctly installed and hasn't expired.

2. **Check Your Certificate Chain:** Make sure your SSL certificate chain is complete and in the correct order. An incomplete chain is one of the most common causes for this error. The chain should include the end-user certificate (server certificate), any necessary intermediate certificates, and the root certificate.

3. **Use SSL Tools:** There are various online SSL checkers available (like SSL Labs' SSL Server Test) that can help you identify any issues with your SSL certificate or chain.

4. **Update Your SSL Library:** If you're using an older SSL library, it may not recognize newer certificates. Make sure you're using the latest stable version.

5. **Check Your Pusher Configuration:** Ensure you have correctly configured your Pusher client and server libraries for SSL. Some libraries require explicit configuration to use SSL.

6. **Firewall or Proxy Issues:** If your server is behind a firewall or proxy, this could also cause SSL handshake issues. Check your firewall or proxy settings to make sure they're not interfering with the SSL handshake.

7. **Consult with Pusher Support:** If the issue persists, consider reaching out to Pusher's support. They may have specific guidance based on their platform.

Remember, it's always good to backup your system before making any major changes. And if you're not familiar with these processes, you may want to consider getting help from a network administrator or a professional with experience in SSL certificates.