Chat profiles aren't synced immediately with your network account; it automatically refreshes every couple hours or so (or when a moderator force-refreshes your chat profile). Especially for the initial 20 reputation to allow you to chat, it's going to take a bit of time for chat to catch up to the main site.
This problem have been acknowledged in these Meta Stack Exchange posts:
chat room constantly re-loading
Chat hanging during load
I'm unable to join chat in Safari on my iPhone when on my mobile network (O2)
Chat channel keeps loading forever
You'll probably have more luck searching for these generic kinds of question in the main meta site.