Some users since being updated to 2.6.0 cannot display the available conference rooms. The “Browse conference rooms” dialog says “Browse conference rooms - null” and displays the following list of rooms but none of ours.
I found that some users conferences list was blank. Having them hit the “+” button added the service and they are now able to see the rooms and not the “null” list. This is different than the 2.5.8 conferences options that we can see.