Adding Let's Encrypt Root CA

Hi.  I am trying to add the Let's Encrypt Intermediate Certificates and they are failing to import.  I was able to import the ISRG Root X1 certificate but not he intermediate certificates.  My certificate is signed by the Let’s Encrypt Authority X1 and I want to use this for my admin portal and cannot select it because it doesn't trust the root CA. 

https://letsencrypt.org/certificates/

I get a generic "Certificate Authority could not be uploaded" error without anything in the logs.

I am hoping this is added in the future (since all modern browsers now trust it) however I would like to add it myself in the interim.

Thanks!