When a Zap is not being used for a long period of time, Zapier automatically disconnects the connection for security reasons.

To reconnect:

Go to your Zaps

Find the Zap that needs to be reconnected, and select it:

Click Edit Zap

Look for the warning message in Zapier "Please connect this account"

Clicking it will open the step that needs to be fixed.

Click "Please reconnect it here"

Publish your Zap if prompted.