The DHCP server is not available is the most likely cause of the issue where a new computer is unable to ping the default gateway. DHCP stands for Dynamic Host Configuration Protocol, which is a network protocol that automatically assigns IP addresses and other configuration parameters to clients on a network. The default gateway is the IP address of the router or device that connects a local network to other networks, such as the internet. Pinging is a network utility that tests the connectivity and reachability between two devices by sending and receiving echo packets. If the DHCP server is not available, the new computer will not be able to obtain an IP address or other configuration parameters, such as the default gateway, from the DHCP server.
This will prevent the new computer from communicating with other devices on the network or the internet, resulting in ping failure. References: [CompTIA Network+ Certification Exam Objectives], What Is DHCP? | How DHCP Works | SolarWinds MSP

The question describes a scenario where a student can connect to the campus Wi-Fi with a laptop, but not with a phone, even when they are close to each other.
This suggests that the problem is not related to the transmission speed, channel overlap, or antenna cable attenuation/signal loss, as these factors would affect both devices equally.
The most likely cause of this connection failure is that the student entered the incorrect passphrase on the phone, or the phone has a different security configuration than the laptop.
To verify this, the student should check the Wi-Fi settings on the phone and make sure they match the laptop's settings, such as the SSID, security type, and passphrase.
If the phone still cannot connect, the student should contact the network administrator or the Wi-Fi service provider for assistance. Reference:
CompTIA Network+ N10-008 Study Guide, Chapter 3, Section 3.1, Wireless Network Standards and Encryption, page 1251 Professor Messer's CompTIA N10-008 Network+ Course Notes, Section 3.1, Wireless Network Standards and Encryption, page 192 Professor Messer's CompTIA N10-008 Network+ Training Course, Video 3.1 - Wireless Network Standards and Encryption, 12:00 - 13:003

Explanation
"Use private VLANs: Also known as port isolation, creating a private VLAN is a method of restricting switch ports (now called private ports) so that they can communicate only with a particular uplink. The private VLAN usually has numerous private ports and only one uplink, which is usually connected to a router, or firewall."

Explanation
"The Data Link layer also determines how data is placed on the wire by using an access method. The wired access method, carrier-sense multiple access with collision detection (CSMA/CD), was once used by all wired Ethernet networks, but is automatically disabled on switched full-duplex links, which have been the norm for decades. Carrier-sense multiple access with collision avoidance (CSMA/CA) is used by wireless networks, in a similar fashion."