Headwind MDM web panel downloads the launcher from its URL, and calculates its checksum. This checksum, together with the launcher URL, is included in the enrollment QR code. A device calculates and verifies the checksum to avoid MDM application interception attack.
The checksum error means that the checksum calculated by Headwind MDM web panel differs from the checksum calculated by a device (using the same download URL!). When your Headwind MDM instance is behind the NAT, this could happen due to routing errors.
See the related issue here: https://qa.h-mdm.com/1/installed-the-system-but-qr-code-is-not-showing
To diagnose the issue, please do the following:
1. Open Headwind MDM web panel, "Applications" tab, find the com.hmdm.launcher application and copy its URL to the clipboard.
2. Open the SSH console to your Headwind MDM instance, and download the URL by using the wget utility.
3. Check the wget output for errors and compare the result with the real APK file.
See the link above how to fix the issue. The most common option is to determine the server's local IP address (should be an Ethernet network interface, not 127.0.0.1!), and add the DNS record (Headwind MDM domain: local IP address) to /etc/hosts.