When a customer attempts to publish their website from within the Weebly website builder, they may encounter the following error message:
Oops! There was an error publishing your site. The publishing credentials are not valid. Please contact support.
This means that Weebly cannot connect to your server via FTP to upload the client's website.
To resolve this error, please update the FTP publishing credentials by following this guide: Setting or Updating FTP Publishing Credentials.
NOTE: Publishing only supports plain FTP. If your server requires FTP/TLS or SFTP, this requirement will need to be removed.