A user reports that a software application functioned as expected the previous day, but this...

Identifying changes made to the system is the next step to troubleshoot why an application no longer launches, as recent changes often cause such issues.

Why Not A (Research the symptoms): Research is broader and should come after identifying changes.

Why Not C (Determine which steps need to be performed): This comes after identifying the issue.

Why Not D (Check the vendor's website): This is a later step if further guidance is needed.

CompTIA A+ Exam Reference: Core 2 (220-1102), Section 3.1, troubleshooting methodology​.