I've had this happen too, with turning network permission on and off again solving the problem. I believe you might only have to do this once.
Every time I did a fresh install of GBoard (I've done that 3 times, each time to test other voice to text alternatives like Sayboard or Google Recorder) and downloaded the offline language files, the "Can't reach Google right now" issue appeared a few days later. It never reappeared again for the few months I continued to use GBoard.
Keeping my finger crossed. I'm back on GBoard and I haven't had the issue appear again for the last two weeks.