You may be getting the following error in WordPress' Site Health check:
The REST API is one way WordPress, and other applications, communicate with the server. One example is the block editor screen, which relies on this to display, and save, your posts and pages.
The REST API request failed due to an error.
Error:  cURL error 28: Operation timed out after 10000 milliseconds with 0 bytes received
Now, although WordPress declares this as critical error, it actually does not affect functionality of your website in any way.
However, this issue can be tackled simply by installing a plugin found here. Once you install this plugin, Site Health will no longer report any issues.