Trying to connect GSX to Jamf Pro, when uploading a .pem file, we receive "Unable to save certificate due to unknown error".

The .pem file needs to be converted to .p12 file.

https://learn.jamf.com/bundle/jamf-pro-documentation-current/page/GSX_Connection.html

Convert the Apple Certificate .pem to the .p12 format. Create a .p12 file using the private key and Apple certificates by executing the following command:
​openssl pkcs12 -export -inkey privatekey.pem -in cert.pem -out GSX_Cert.p12

Now you may be receiving "unable to load file" error when uploading GSX certificate as .pem in Jamf Pro.

The GSX upload button within Jamf Pro shows .pem and .p12 as valid upload options. Only .p12 files will work.

Create a .p12 file using the private key and Apple certificates by executing the following command in Terminal:

For more information on GSX, see the Integrating with Apple's Global Service Exchange (GSX) Technical Article.