1. Make sure the theme, xstore core plugin and the woozone plugins are all up-to-date.
2. If step 1, okay and still the issue happening means, can you try disable all the other third-party plugins you installed, and see something that cause the issue.
3. Make sure the plugin’s styles are not removed by your server automatically? ( You can download the plugin manually using https://www.8theme.com/download-plugins/ and then check any folder or file is missing when the error happens. )