When a technician is unable to connect to a laptop over a VPN, one of the most common reasons is that the firewall settings on either the laptop or the network are blocking the connection.
* Wireless protocol: Unrelated, as the technician is already connected to the VPN.
* DHCP pool: Unlikely to be the issue, as it deals with IP address assignment.
* Content filtering: Typically involves filtering web content, not affecting direct connections.
* Firewall: The correct setting to review, as it may block the necessary ports or services required for remote access.
Reference: CompTIA A+ Exam Objectives [220-1102] - 2.3: Given a scenario, troubleshoot common wired and wireless network problems.