Server Essentials Anywhere Access not trusted cert

Hi,

I have an issue with importing my ssl cert into the anywhere access wizard in Windows server essentials 2016. I have followed this guide and successfully generated a certificate - https://www.server-essentials.com/support/get-a-free-lets-encrypt-certificate-anywhere-and-automatically-renew-it

However when I try to setup Anywhere Access in the wizard, it gives me an error that the SSL cert isn’t trusted. I have looked at similar topics online and that hasn’t helped. I have letsencrypt in the Trusted Root Certification Authorities and have tried manually adding it again too. I have the latest server updates and have restarted the server. However it just won’t accept the cert as trusted.

Has anyone else had this issue more recently or can help?

Thanks