Hi!

No, the scenario was built with the base game without any content of the latest add-on, so I guess this should not be the reason why it doesn't turn up in-game.
Other download scenarios work for you without any such issues, I assume?

Thank you for your answer, but unfortunately no. I check on several another scenarious from workshop and same result. Community tab empty. But still start up of the game I see message downloading user content ... Any advices will be helpful. Fot example, do you know there are community maps should be placed in filesystem? I ca try check manually

So if this issue is not restricted to my scenario, it seems like a more general issue.
I haven't downloaded any scenarios so far so I won't be of great help therefore.
There is a basic "How To" guide about uploading and downloading
http://ageofwonders.com/sharing-user-content/
but it seems to be very scarce on information about downloading stuff.
My best advice would be to make a posting in the general tech issues forum here on steam or on the age of wonders 3 forum. Hope you can sort this problem out quickly.
Cheers.

I've find out reason and now playing. Thank you for your hard work! :) Which level of AI you recommend to use?

Good to hear you could solve the installation issue.
As all cities are pre-built in the scenario, there is less room for the AI to "mess up" by building unnecessary buildings instead of armies, so I feel that the AI is a bit more challenging overall compared to standard AoW scenarios or random maps.
Depending on your familiarity with the Illuria scenario and your general experience and skill with AoW3, I suggest "Medium" or second highest (King?) difficulty level for your first play on this map. Cheers.