wifi is greyed not working after restore
ipad air 2 wifi not working after replacing lcd and restoring
Did you make sure you didn't cut the wifi cable? Saying that, cutting the cable usually doesn't cause it to be greyed out.
Did you restore because it was greyed out? That wouldn't solve a hardware issue.
You most likely cut the wifi cable upon removing the digitizer. This can be very difficult not to do. Pull the digitizer back up and inspect the cable that is screwed to the frame to the right of the home button. See attached picture for location.
Try to disconnect the battery for one hour and then connect it again. Restore and everything should be cool.