import demo files wordpress

After testing wordpress multisite and its operation, install the theme “education lms”. In order to do a test, when you click on import demo data, it sends a message after a while loading, error bad gateway (502). What can be?

Nginx 502 - Bad Gateway Error

the site is new with no plugins, I only make an import of the test data of the theme

@tonyway said:
the site is new with no plugins, I only make an import of the test data of the theme

The issue isn’t about installing new plugins. If you checked the article, you would know that this may happen because

your website code takes too long to generate a page

This could be a new plugin installation, but it could also be a script which is doing a large, slow data import causing the problem. It’s likely that the demo content you’re uploading just takes too long to set up.