You have implemented an AP at a remote office. It is a single-band AP supporting 802.11ac. Several users complain that their laptops cannot connect to the WLAN. These laptops are from multiple vendors and range in age from 2 to 4 years. The SSID and security profile settings are correct. All default settings were used on the AP with the exception of the SSID and security settings.

What is the most likely issue preventing these STAs from connecting to the AP?