Error - “The operation failed for an undetermined reason. Typically this problem occurs due to certificates that the browser does not trust. If you are using self-signed or custom certificates, open the URL in a new browser tab and accept the certificate, then retry the operation.”
Open vCenter Server address in a browser. https://vCenterServerName.DomainName.com, not the complete vSphere web client address.
Click on Download trusted root CA Certificates.
Unzip the download.zip file
Open the folder according to your Operating System
In my case, some of them are already installed, and others are not.
If you have many files in the operating system folder, then sort it according to the file type
Double click on the .crt files and click on Install Certificate
On the ‘Certificate Import Wizard’ , Select Local Machine and click Next
On the Next Screen, Select ‘ Place all Certificate in following Store’ option, and Select Trusted Root Certification Authorities by clicking the browse button.
Click Finish and do the same for the rest of the certificate.
Restart the browser, and you should be able to upload the files.