How to fix 'Unable to get checkpoint buffer' error in Heimdall?

This error can be attributed to a variety of issues. Here are some steps you can follow to troubleshoot:

1. Check Heimdall Service: Ensure that your Heimdall service is running correctly on both your sentry and validator nodes. If the service has stopped unexpectedly or if there are any errors, try restarting your Heimdall service. See if the issue resolves after the restart.

2. Review Bor Service: Look into your Bor service for any unintended halts or error messages in the logs. A restart of the Bor service might resolve the problem.

3. Examine Heimdall Bridge: Verify if your Heimdall Bridge is up and operating without any errors as shown in the logs. Restarting the Heimdall Bridge service might also fix the issue.

4. Configure ETH_RPC_URL: Check the heimdall-config.toml file to ensure that the ETH_RPC_URL is configured correctly. Update the URL if it’s not correct and then restart Heimdall.

5. Seek Support: If none of the above steps fix the problem, it may be necessary to contact the Polygon support team for further assistance. You can submit a support ticket via this link.

These steps are based on common troubleshooting practices and further details can be found in the Polygon Technical FAQs.