This error can only be triggered when using the plugin commands: Change Default Font or Change Font.
So first thing is to find the plugin command that is giving you this alert. Check if you have any common events that are using these commands or any event that is using it on the map start.
After that, the problem is that the Font Face / Index provided on the plugin command, does not exist. You can take a look at your Fonts plugin parameters and compare with the one you set on one of these plugin commands. If you still didn't manage to find the issue, show me a screenshot of your fonts plugin parameter and a screenshot of the plugin command so I can see and compare to check what is wrong.
