Bosand Ya, that's the new quirk - you cannot request control (I've been told this is temporary, but it's been the only way for this new app for a long time now) - the presenter has to go to their control panel and give you control. Only once they've given you control will the mouse icon show up for you, which you then have to click on to actually 'pick up' control and be able to move the mouse/type/etc......
The problem is that if they don't have the right app downloaded/installed, even though the mouse is present when they give you control, you can do nada. IMO, if there is incompatibility between the host and client builds, the mouse shouldn't show as an option to be given, since the web-app has no capacity to give/accept remote control of the mouse/keyboard (from what I understand).
The question you have to ask them is if they see a white box with black G logo - also, you'll want to have them go into add/remove programs and uninstall the older connector (orange box with white asterisk).