Alert:
A bug in MetaMask version 12.15.x caused signature failures across dApps, including GRVT signing. This issue has been resolved in MetaMask v12.15.2, which is now available on the Chrome Web Store.
Recommended Fix
Update MetaMask to version 12.15.2 via the Chrome Web Store.
Sometimes Chrome does not auto-update extensions, so you may need to trigger the update manually:
Steps to Manually Update MetaMask
Open Chrome and go to:
chrome://extensionsEnable Developer mode (toggle at the top right)
Click "Update" (top left) to force an update for all extensions
Confirm that MetaMask is now version 12.15.2
Alternate Workarounds (if needed)
If for any reason updating is not possible:
Export your private key and use a different wallet temporarily
Or uninstall MetaMask and manually reinstall version 12.15.2 from the Chrome Web Store