Disabled scanner


I am quite a new guy in IMLT, so i have two basic questions:

First: I have tried to install Endpoint manager clients on four machines (3 servers, 1 PC).
Now i would like to install scanner to all of them, but my endpoint manager allows me to
install only two of them (1 server, 1 PC).
I have noticed, under the scanner information, it is “scan disabled” and in my case,
I can see “true” value for two servers - but i didnt disable anything. And now I dont know where/how should I enable the scanner. I would be grateful for any advice.

Second question: When i tried install scanner on PC (Win 8.1) it take too long and ends
with “evaluating”. Is it because scanner can be install just on server OS?

I cannot upload any pictures, so i hope my description is accurate.

Thank you,