When I draw for activation and no symbol matches (still more than two Killer EU on the board)...It happened to me as well and decided that the Killers pass and nothing happens.
1. Draw another card?
2. Pass this impulse and draw another card next impulse?
For this one there is a rule page 8
Also, if a unit with a marker moves into a square with another MM, do they each retain their own activation marker? Or does one give way to the other? Sometimes the rules speak of activating a "square", which would mean all the units in that square. But if there are two activation markers... ?
If all units under a revealed MM are eliminated, the MM is removed. A revealed MM moves with the units beneath it. If a revealed MM and the units beneath it enter a square with another revealed MM, discard one, randomly determined MM.
So an unrevealed MM always remains in play until revealed even if they share a square with another MM, but if two revealed Killer units share the same square, they also share 1 of the 2 MM, the other being discarded.