Site health: Page cache is not detected and the server response is slow

I’m getting this critical issue in my site health and its not clear what I need to do. Anyone know?

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Page cache is not detected and the server response is slow

Page cache enhances the speed and performance of your site by saving and serving static pages instead of calling for a page every time a user visits.

Page cache is detected by looking for an active page cache plugin as well as making three requests to the homepage and looking for one or more of the following HTTP client caching response headers:cache-control, expires, age, last-modified, etag, x-cache-enabled, x-cache-disabled, x-srcache-store-status, x-srcache-fetch-status.

•  Median server response time was 623 milliseconds. It should be less than the recommended 600 milliseconds threshold.
•  No client caching response headers were detected.
•  A page cache plugin was not detected.

Learn more about page cache(opens in a new tab)

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