The first step in any debugging process is information gathering. Do not rely solely on the boot splash screen.
The script may require the PCI bus to be enumerated, sysfs to be mounted, or a particular kernel module to be loaded first. If systemd runs the script too early, loading fails. The first step in any debugging process is
Based on real-world reports from server logs (Red Hat Bugzilla, IBM forums, and Stack Overflow), the following are the primary reasons for this error: sysfs to be mounted