The "Give project" text field placeholder says "Start typing to search users", but nothing happens when typing into it. (Similar field works in the "Add user" view.)

On which pagure instance are you seeing this behavior? If you wait a little
while does it finally shows up?
Finally, if you were to check the network tab of the firefox web-development
toolbar, do you see any request failing?

Thanks :)

Seen in all instances I have access to: pagure.io and src.fedoraproject.org.

I just tried pagure.io with Chrome Devtools, and typing into the field doesn't make any requests at all.

Quite probably related:

Going to https://pagure.io/mailcap/settings gives me this in Chrome's Console:

settings:1304 Uncaught TypeError: $(...).selectize is not a function
    at settings:1304
(anonymous) @ settings:1304

Selectize JS and CSS seem to be missing from the settings view.

Commit 441613c8 fixes this issue