Most likely the issue is that your computer time is not synchronized with the internet time. This is how to fix this:
On your Mac, choose Apple menu > System Preferences, then click Date & Time.
Click Date & Time, then set the date and time automatically.
Go to Start > Settings > Time & language > Date & time.
Then set time automatically.
Make sure you are connected with Metamask on the ETH mainnet.
Try with Chrome or Firefox browser.