Hi,
We support 3 types of 2g authentication comp128 v1, comp128 v2, comp128 v3. The interface assumes that v1 is used since this is the most common. Maybe your sims use one of the other. You should check the sims specifications.
There is also a 4th type that was later added, but we don't have support for it.
To use another comp128 version you must edit subscribers.conf by hand and set op=2 or op=3 for each subscriber.