Hi Ming.
Please do not use an old deprecated UCS distribution.
User administrator or user in the administrator group?
After installing EGroupware, you will be shown instructions.
Here also in the app description:
I had written an article about EGroupware on UCS. Unfortunately, it has not yet been translated into English. Try it with a translator of your choice:
I have moved your article to the right category
Rocket.Chat => EGroupware on UCS
Stefan