[xwiki-users] In the XE Manager, how is the control site selected?

I tried to upgrade my XE version to XEM. I got it working. I setup 5 sites plus what I call the "control" site. Everything seemed to be going well until Last night. One of the Farm sites (1 of 5) is no longer displaying it's home page correctly. When I type in it's url, It displays the "control" site. The other 4 farm sites come up ok as usual. How do I fix this? Is there some parameter someplace that identifies the wiki site that is The control site and which ones are farm sites? Please advise. Lee