Exporting the root certificate does what it states - it simply exports the certificate as a file (to your Desktop directory). Howver, you still need to install the exported certificate manually (as the automatic installation fails for some reason).
Start Fiddler Everywhere and go to Settings > HTTPS. Expand the Advanced Settings sub-menu and use the Export root certificate(DER/Binary format) from the drop-down menu. The certificate is exrpoted to ~/Desktop as file with name FiddlerRootCertificate.crt.
Install the certificate in the OS certificate manager. Detailed steps described here: https://docs.telerik.com/fiddler-everywhere/knowledge-base/how-to-install-fiddler-root-certificate-on-windows
Restart Fiddler Everywhere and enable Live Traffic capturing
In case, the issue persiste then you can send us your Fiddler application logs (Help > Open Application Logs Folder) to support at getfiddler.com.
click "Trust root certificate" tips “Fiddler Root Certificate NOT trusted successfully.”
then click "Export root certrificate(DER/Binary format)"
then click "Reset root certrificate"
But still tips “Fiddler Root Certificate NOT trusted successfully.”