Slitherine

No matter how much I try to get the summon spell to actually work, all that happens is:

I get the "summon" pop up screen.

I click on "summon"

I see hexes where it could be deployed...

but no matter how much I left or right click, it never deploys.

What am I doing wrong?

If you have this problem again could you get us some more detailed information descripted here.
Especially the output_log.txt and a savegame from just before trying to execute it.
How it should work
* Choose a unit from the menu
* Left click summon
* Place cursor over a tile that it shows you
* Cursor should be green
* Right click to execute like for any other skill.