When attempting to import an existing server certificate into Portal for ArcGIS or ArcGIS Server using Internet Explorer, the import process fails, and returns the following error:
Error: Unable to import certificate. Code: 500
Internet Explorer Enhanced Security Configuration (ESC) is enabled, preventing the certificate from being imported into Portal for ArcGIS and ArcGIS Server. Refer to Microsoft: FAQ about Internet Explorer Enhanced Security Configuration (ESC) for more information on ESC.
Disable the Internet Explorer Enhanced Security Configuration setting in Windows Server Manager, and reattempt the import process.
Note: Alternatively, import the certificate using a different web browser, such as Google Chrome.