Subdomain on Subfolder install?

Not sure if this is a host issue or maybe rewrite rules issue? Have a subfolder multisite install running 5 sites each with their own domains. Need a new site, and this one uses a subdomain, but the sub is a based on a domain that’s running on a completely different server, not a sub of any domain running on the multisite install. Install went fine, can access the WP backend for the subdomain, but the front end just displays a blank screen. Tried uploading a graphic just make sure the folder was there, it is, and I can access the graphic using the full subdomain’s URL. What am I missing on the front end? Thanks in advance.