I just had a similar situation with my MacBook Pro. It started on a black screen that said Activate Mac across the top and "Recovery Assistant" in the menu bar. It was asking me to connect to the Internet with either WiFi or Ethernet. But there was no wifi menu available nor a wifi symbol near the upper top right corner of the screen, only an A icon and a battery icon.
After digging through a handful of almost-helpful articles online, I found one that did the trick. It said to hold down the physical power button on the Mac until it powered off. Wait 30-seconds, then power it back on.
As I did so, there were a couple of odd schematics that showed up during the reboot (one looked like a mouse from the bottom, the other looked like a menu bar in miniature)… but eventually, I ended up at the Activate Mac screen again AND the wifi icon was in the upper right corner of the screen. That allowed me to manually enter my network name and password under the "Join Other Network" option.
I hope this helps…
Ron