Make sure its armed, not jammed and that you have 25 energy to your name and the needed oil amount to send it where you want it to go.
adding 24 control ticks on that
1 you must have 24 control ticks on silo,
2 it should be armed, target in 24 ticks,
3 Target can't be your allies things
4 nor Admin's (like relics, Garrisons, wreckages etc) ,
5 you must have 25 energy and
6 Oil/lumber/gas over 90 ...
7 Silo shouldn't be jammed...
[ minimum ETA of a missile is 6, can't be less, so u must have 90 oil. as 1 ETA take 15 oil/lumber/gas.]