Ok, the Roon Rock is on the same network with a Mac Mini (on a same switch), the Mac Mini is no issue at all, I can login Roon and works pretty well. Yes, I can access the Rock web UI with no issue, it is just not able to login my Roon account with my Rock, I moved my Rock to other place with differnct network but with the same result.
The Rock used to work pretty well, yesterday when I tried to login, a warning pop up saying that it was linked with too many computers, therefore, I log out and failed to log in again.
I have done the Restore, which did not help, then forced me to reinstall the Roon Rock software , badly I got a installation problem (please see my another post) Kernel Panic while installing