Open: https://play.google.com/console and click on the application.
Click on Policy and programs → Policy status
And here is this message: Privacy Policy section of the User Data policy: Invalid Privacy policy
URL provided https://... does not link to a valid privacy page

 
Step 1. Creating a new website
Create a new one-page site using sites.google.com ...
I wrote the following text:
privacy_policy_source.png ...

Step 2. Save the site on the server
Click Publish to save the site to the server.
Specify the path, for example: melonapp
And click on Publish at the bottom

 
Note!
Now the site after clicking Publish is located at the web path:
https://sites.google.com/view/melonapp/
 

 
Step 3. In the Google Play Console, we will install a new site
Open: Monitor and improve → Policy and programs
Or you can open it like this at the end: /app-content/privacy-policy

Let's write the address of the new site:
https://sites.google.com/view/melonapp/

Press the button Save

 
Result:
There is no error in Google Play Console.