My mac pro just crashed & my wifi won't connect

MacBook Pro mid 2014, 2.2 Ghz, Intel Core i7, 16 gab 1600 MHz Ddr3, OS X Yosemite. Was online & computer crashed & restarted, sent a report to Apple. There was no wifi connection & the upper bar said wifi: no hardware installed. I rebooted both the computer & my router, with no different result. Odd that when I reboot Mail is open which I didn't have open.