"Undefined" error when loading templates

If you see an "Undefined" error message when you try to add a template:

• Actualice su versión de PHP a PHP7 (haga una copia de seguridad de su sitio Web antes)
• In some cases, the latest version of PHP can cause undefined errors. Although staying up-to-date with PHP versions is often a good idea, it can cause problems in extreme cases. Downgrade PHP to a version lower than latest if this occurs.
• Pídale a su empresa de alojamiento que aumente el valor de tiempo de espera de su server
• Also ask them to verify the encoding of the database.
• Verify that it is not due to a plugin conflict by disabling all your plugins in addition to Elementor and Elementor Pro. If this solves the problem, please reactivate them one by one to find the culprit.
• Compruebe si no se debe a un conflicto con un plugin of browser editando en modo incógnito con su navegador.