Occasionally when waking my laptop from sleep, wifi is disabled. It’s usually some kind of weird driver bug where the card refuses to reinitialize properly. In the past, I’ve just unloaded and reloaded the appropriate kernel module and that would cause it to load correctly.
However, this doesn’t seem to work on my laptop at work. Some googling found a page with the command “rfkill list all” which shows the list of devices on your computer that broadcast some kind of wireless signal (wifi or bluetooth). “rfkill unblock all” reenables all devices, which fixed my issue.