Explanation
The best practice for troubleshooting is to follow a logical and systematic process that involves identifying the problem, establishing a theory of probable cause, testing the theory, establishing a plan of action, implementing the solution, verifying functionality, and documenting findings. Since the problem occurred after a change in the server's BIOS, the most likely cause is that the change was incompatible or incorrect for the OS. Therefore, the next step should be to reverse the latest change made to the server and reboot to see if that fixes the issue. References:
https://www.comptia.org/training/resources/exam-objectives/comptia-server-sk0-005-exam-objectives (Objective 4.3)