Artifacts in Artifactory have Client Checksum and Server Checksum. Server Checksum is calculated by Artifactory while Client Checksum is provided by the deployer.
You can refer to this article for more details on Client Checksum, Server Checksum, and Checksum Policy
In a case where a Client's Checksum is missing and your Checksum Policy is Client Checksums. You will see warnings “Client did not publish a checksum value…”. You can also fix the checksums individually in the UI.
However, if you have many existing artifacts with missing client checksums, you might need a scaleable solution.
You should first try to verify how you are deploying your artifacts and check why is client checksum is not deployed so that newly deployed artifacts do not have the issue.