I have just received my new UR824 interface and I have installed drivers, soft and the included Cubase 7 AI.
I read it was able to manage up to 64 audio tracks ( http://www.steinberg.net/fileadmin/files/PRODUCTS/Cubase/Generation_7/Cubase_7/Downloads/Cubase_Comparison_Chart.pdf) but it gets stuck at 32…well, its strange, but I read in the web it´s 32 channel limited.
Ok, it´s just something Steinberg should correct.
Then I see the new Cubase 8 AI version, which is able to use the promised 64 tracks, so I buy the upgrade, get the code, download and install the soft…and when I´m trying to paste it in the eLicencer soft utility it tells me there is no suitable software to upgrade.

Can somebody help me?

The link you posted compares Cubase Elements, Artist and Pro…AI is not on this comparison table??

There is no upgrade path from Cubase AI7 to AI8 that I can see…where did you buy this & what exactly is the name of the upgrade??
EDIT: In fact I’m pretty sure there is no such thing as Cubase 8 AI…you seem to be confusing the different versions and I guess you may have bought the wrong upgrade??

I have Cubase 8 AI though not sure it was available at time of OP.

Try posting your question in the AI forum, and for licensing problems Steinberg support should be able to help.