Errors: REST API gave an error, Your site could not complete a loopback request on one of the hosts with the same site, how to fix it?

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Errors: REST API gave an error, Your site could not execute a loopback request on one of the hosts with the same site, how to fix it?
There is the same site on two hostings, one is test, and the other is where the site should work

like this on a test:

like this on the second:


php versions are different, but they were the same at the time of the error, I updated in an attempt to remove the error
Even in PageSpeed ​​Insights, the second one gives the following error:
Lighthouse returned error: FAILED_DOCUMENT_REQUEST. Failed to load page. Make sure the URL is entered correctly and the server is responding to all requests. More details: net::ERR_TIMED_OUT.Close

I don't know if it's important, but it's only when I check the https version of the site, if I enter http, then there is no error.
And the test site does not have a certificate at all at the moment.
The second site has a certificate from Let's Encrypt, received through the hosting panel, and the second site worked fine for 15 days, but today there is such a problem
. Tell me, please, what could it be?
I suspect it's a hosting issue.

Answer 1

Hello!
1) a problem with hosting
2) exclude CORS, since it doesn’t work for you via https, but it works via http. Maybe you are serving static via http, which is why CORS occurs in the https version
. To begin with, exclude this.