Ok,I managed to reach that tower and after saying to all these three companions to start the event.The fireworks start, but the quest log still says I have to trigger the gala event. The map also points back to the tower. Is there any way to fix this?
And by the was Great Forum!

Ok,people please help me! Is there any way to fix this?
I also heard that you can walk to doors that lead to casino and use some command like unlock but I am confused how to do that? Please help!

It sounds like a script isn't being triggered propperly, I would suggest reloading to a previous save then hopefully it wont keep glitching.

If that dosn't work, you could try the console command that you brought up. To access the console, press the backquote key ( ` ) when unpaused, the button is different depending on where you are from and the make of the keyboard. If you are using a keyboard from US press the ( ~ ) key to access console, if you are using a keyboard from the UK press the ( ? ) key which is usually just above the Tab key.
Now that you have the console open, click the gate to Sierra Madre to select it and type "Unlock" then hit enter, now the gate will be open for you.
I'm not sure forcing the gate to open with a console command will continue to game, but you can always try.

Hope this helps.

Hey,that helped thanks but I got another bug.When at the end of the game I open vault elevator and go in it there is door in front of me that is open.
But when I try to open,nothing happens and I cant go on,what should I do?