I’m working on a React application and trying to integrate EmailJS with Gmail for sending emails. After setting up my Gmail connection in the EmailJS dashboard and providing the ‘Send email on your behalf’ authorization, I keep running into this problem:
412 Gmail_API: Invalid grant. Please reconnect your Gmail account
I’ve attempted several troubleshooting steps:
Removed and re-added my Gmail account in EmailJS settings
Verified OAuth permissions are properly set in my Google Account settings
Double-checked all API credentials and Service IDs for accuracy
Despite these efforts, the same error keeps appearing. Can someone explain what this ‘Invalid grant’ error actually means and provide a solution? What’s the correct way to reestablish or refresh the Gmail authorization for EmailJS?
Had this exact issue last month! my Gmail token expired after 7 days of not using it. Go to your Google account security settings, revoke EmailJS access completely, then reconnect it fresh in the EmailJS dashboard. Also check your system clock is synced - OAuth tokens are picky about time and being off by even a few minutes breaks things.
This error usually happens when your token gets corrupted or there’s a scope mismatch between Gmail and EmailJS. When I hit this issue, it wasn’t actually EmailJS - it was my Google workspace settings. If you’re using a workspace account, log into your Google Admin Console and check that third-party app access is turned on. What fixed it for me was signing out of all Google accounts in my browser, then signing back in with just the account I wanted for EmailJS before reconnecting. Multiple Google accounts logged in at once can mess with authentication and trigger the invalid grant error even when your credentials look fine.
The Invalid grant error typically indicates issues with your OAuth credentials. This could be due to an expired refresh token, a recent change to your Google password, or if Google detected unusual behavior from your account. I encountered a similar error previously, and clearing the browser cache resolved it for me. This step helps because outdated authentication data can interfere with new authorization attempts. Also, ensure that you are using the correct Google Cloud Project credentials in EmailJS and check if your account has two-factor authentication enabled, as it may require an app-specific password.