Resolving 'Keystore contains an entry whose alias is not acceptable for import' Error in Salesforce Certificate and Key Management

To resolve this error, find the current certificate alias and change it to one that meets Salesforce's naming requirements.

Step 1: Find the Current Certificate Alias

Use the Java Keytool command-line utility to list the certificates in your .JKS file and identify the current alias name:
keytool -list -v -keystore C:\Path_To_JKS\Name_of_JKS_file.jks
In the output, look for the "Alias name" field. The value shown must comply with the naming requirements listed in the Description section above.

Step 2: Change the Alias to Meet Salesforce Requirements

Once you have identified the non-compliant alias, use the following Keytool command to rename it:
keytool -keystore C:\Users\USERNAME\Desktop\FOLDER\filename.jks -changealias -alias EXISTING_ALIAS -destalias NEW_ALIAS
Replace EXISTING_ALIAS with the current alias name and NEW_ALIAS with a new alias that meets Salesforce's naming rules (starts with a letter, alphanumeric and underscores only, no trailing underscore, no consecutive underscores).
Enter the keystore password when prompted.

Step 3: Retry the Import in Salesforce

After successfully changing the alias, return to Salesforce Certificate and Key Management and retry the Import from Keystore operation with the updated .JKS file. The import should now succeed.