General Connectivity: Have you tried the following?
Have you unplugged and re-snapped the cable in at both the PC & wall?
Are the ends of the network cable in good shape (have working clips)?
Have you replaced the cable?
Have you moved the device to a different wall jack?
Did moving it to another wall jack work?
Have you tested with your test PC?
Did you disable wi-fi before testing with the test PC (if hard-wired connection issue)?
Did the test PC work?
Is wi-fi disabled or enabled on the computer?
If plugged in - is the computer plugged in to the phone?
Does the phone work in the office?
If plugged in, click Start and type cmd in the box that pops up, type ipconfig - What is the IPv4 Address listed?
Have you power-cycled/rebooted the device?

Advanced Networking: Have you tried the following?
Does the computer have a VPN turned on/connected?
Is there a firewall/router in the office or one specifically for this user in the equipment room?
Is the device plugged directly into the wall or into a switch or other device?
Have you tested the wall jack with a laptop to see if you can get on the internet?
If trying to print to a printer inside this office, how is the printer connected?

Additional Troubleshooting Completed
Have you tested plugged directly into the wall jack?
Unplugged & re-snapped network cable (both ends)
Replaced network cable
If hard-wired, have you disabled the Wireless adapter?
Have you tested with another computer/device?
Did the second device work?
Yes, 2nd wall jack is working
No, 2nd wall jack not working or not available
Are you connected to a VPN (software)
Wi-Fi - Are you connected to the Guest network?
Wi-Fi - Are you connected to the company network?
Wi-Fi - Does wireless work for others in that area?
Wi-Fi - Is the wireless adapter disabled on your computer?
Wi-Fi - Is the issue with Wi-Fi on a phone?