I know this post thread is a little old but I though I would just mention this. Last night I was trying to get a Minecraft server setup and for one reason or another I ended up going into msconfig and disabling most of my startup services. Then of course today I was getting this error when I tried to open Maya.

License was not obtained.....

FlexNet is a required service for license verification and has to be running in order to launch Maya. The quick fix without a restart was as suggested above going to

Start->Services

Then scroll down until you find FlexNet and double click. Set it to automatic then close that window then reopen FlexNet service and the start button should now be available. Press Start and viola Maya runs.

Don't forget to check mconfig just to verify that FlexNet is set to startup with the computer to avoid this problem.

FYI if you have a 64bit you might have two FlexNet I have them both enabled though I'm not sure if they are both required. Or perhaps one of them is for Maya and the other for Photoshop I think both companies use FlexNet Licensing Services.