The most likely reason is A. Missing Wi-Fi adapter.
A Wi-Fi adapter is a device that allows a computer to connect to a wireless network. A legacy workstation may not have a built-in Wi-Fi adapter, or it may have an outdated or incompatible one. If the workstation does not have a Wi-Fi adapter, it will not be able to detect or access any wireless networks, regardless of the location, signal strength, or configuration of the network.
To fix this issue, the technician can install a Wi-Fi adapter on the workstation, either internally or externally. An internal Wi-Fi adapter is a card that fits into a slot on the motherboard, while an external Wi-Fi adapter is a device that plugs into a USB port. The technician should choose a Wi-Fi adapter that is compatible with the workstation’s operating system, hardware, and wireless standards .
The other options are less likely to be the reason for the issue. A Wi-Fi AP replacement means changing the wireless access point that provides the network connection. This may affect the network name, password, or settings, but it should not prevent the workstation from detecting any wireless networks. A hidden Wi-Fi SSID means that the network name is not broadcasted publicly, but it can still be accessed by entering the name manually. A hidden Wi-Fi SSID may make it harder to find the network, but it should not prevent the workstation from detecting other wireless networks. An incorrect Wi-Fi channel means that the network is using a frequency band that is crowded or interfered by other devices. This may affect the network performance or stability, but it should not prevent the workstation from detecting any wireless networks.
References:
How to Add Wi-Fi to a Desktop Computer - How-To Geek
How to Choose a Wireless Adapter for Your Computer - Lifewire
Troubleshooting Wireless Network Connections - Intel