2002 Suzuki Vitara 4wd 4H not engaging

This only became a problem this current winter…Transfer from 2H to 2H slides smoothly and the green 4wd dash light comes on, and the front drive shafts turn but the acuator pump does not engage the frontwheel hubs(and the car remains in 2wd). When in 4L, the dash 4wd light comes on and the acuator pump engages the front wheels giving 4wd - but only at low speeds.

The acuator pump was frozen a few weeks ago, that was removed, serviced and now appears to be giving the correct air pressure to activate the front hubs.

However, since 2L works but 2H doesn’t, is my problem a linkage problem in the transfer case?

If the front drive shafts are turning, the problem is not in the transfer case.