How to troubleshoot a Vauxhall Vivaro that won't start?

I have a Vauxhall Vivaro that won't start. What could be the possible issues and how can I fix them? I've already checked the battery and it seems to be fully charged.

Firstly, try checking the connections from the battery to the starter motor. Make sure they are secure and free from corrosion. If they seem to be in good condition, then it's possible that the issue lies with the starter motor itself. If so, it may need to be replaced or serviced.

Another common issue with Vauxhall Vivaro models is a faulty fuel pump. Check to see if you can hear the fuel pump engaging when you turn the key. If you don't hear anything, then the fuel pump may need to be replaced.

If you've ruled out the battery, starter motor, and fuel pump, then it's possible that the issue lies with the ignition switch. This can sometimes get stuck or worn out over time. You may need to replace the ignition switch to fix the problem.