Server Essentials Anywhere Access not trusted cert


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 -

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?