What you doing is called a "migration" ... move moodle to another server ... and am guessing to avoid having to go through 'painful' steps of upgrading, you've chosen new version of moodle on new server, then restore courses, etc. How many courses? Then change config file URL to old URL to server - thus keeping the same fully qualifed domain name (FQDN).
And, it appears you've tinkered with restore of a course that had links to files that now don't work ... even though you have manually re-created the symlinks in file system repository.
And, I am assuming linux ... right?
A couple of catch 22's (issues):
Does your new server (assuming apache) have followsymlinks setup correctly? Compare apache config of old server with new server.
Moodle uses the wwwurl config line to populate internal links to files.
What are you using to work on new server? URL ... by IP or by another FQDN?
Plus, is your current site using https? Thus certs for server ... commercial or letsencrypt?
Nothing is ever simple!
'SoS', Ken