i have a problem, because i want to install a b737-700 livery from econair with the livery manager ,but he gaves me the message: unknown variety 

Does that particular livery come in the form of a .ptp file?

yes,it comes in a .ptp file

And you're using the 'livery manager' that came with the PMDG NGX to attempt to install it? Also make sure you've unzipped the file if it came zipped and make sure your attempting to install it on the correct model ie. -600 -700 -800 -900 and with or without winglets.

i have did all the things you said , but dont helps

You must be the administrator when using the livery manager. Also check the box for "show all variations" within FSX at Aircraft/Select aircraft. That did the trick for me.

 

Hope it helps,

John