has one apple distribution certificate but its private key is not installed

seriously ? no one ?

well, i contacted the apple support and they give me this solution if any what facing the same problem

"
After investigating into your query, I’ve found that if you didn't back up your private key, you need to create a new private key and then revoke all current certificates. After you've completed these steps, you can issue new certificates for development and distribution.


For information on how to create a private key and new certificates, please reference the Create, export, and delete signing certificates section of Xcode Help.


Revoking development or distribution certificates does not affect applications that are already available on the App Store.


You can continue to submit application updates to the App Store with a new distribution certificate. When your development certificate expires, your application will no longer run on your device. Additionally, applications distributed via ad hoc distribution will stop running after your distribution certificate expires.

Furthermore, if a signing certificate, or private key is missing, please review the following Xcode Help page to learn more about your options.

https://help.apple.com/xcode/mac/current/#/devd1432da9a

"

UPDATE :
update from os from mojave to catalina without losing data didnt solve the problem for me
but when i reset the catalina os from scratch did solve it !
hope this is helpful

I had the same issue. To resolve I had to close Xcode to get it to recognize the certificate and look at the keychain again.

I did everything but my problem is not solved