Welcome to Android Central! Sorry, are you saying that when you toggle the keyboard to show numbers and symbols, it's just blank? Try going to Settings>Apps, select Gboard, then Storage, then Clear Cache/Clear Data. Now see if the problem persists.
All of my devices are messed up suddenly wutb this toggle key on GBoard. It switches to a calculator. In addition GBoard is not correcting spelling properly and is sucking batteries dry like a thirsty vampire.
Worst is the toggle key....it's unbearable. I've even factory reset two devices (pure Google). Same issue.