The script looks okay to me. There is an eject and an unassugnVehicle.
single groups and using a uh-60, but it does not seem to work with chinooks
I take it it does not work for even one group from a chinook?
My thoughts are:
Check how you are calling the script. For example:
give two infantry groups a name: Put
Grp1 = group this
In the init field of one guy in one group and
Grp2 = group this
in the init field of one guy in the other group.
Call the Chinook CH1
Run the parachute script something like this:
[Grp1,CH1] exec "Paradrop.sqs"
~(count units Grp1) + 2
[Grp2,CH1] exec "Paradrop.sqs"
The middle line will delay the drop of the second group until 2 seconds after the first group have finished dropping.
Or if you don't want to put this in a script you could use a trigger to drop the first group and a second trigger (with a delay) to drop the second group.