I think the easiest test procedure would be-
1 - disconnect line that comes from compressor housing and goes to actuator (very short)
2 - attach a pressurised air feed to the actuator - does the actuator arm move? - if yes then the hose you just removed must have been leaking, and may be cracked, or the outlet from the compressor housing is blocked. if no, continue...
3 - can you hear air leaking from anywhere? if so find the source of the leak (should be fairly easy) and repair (it may be the actuator leaking, in which case replace it), if no, continue
4 - if you grab the actuator arm can you get it to move out from the actuator? should only be a cm or so. If no, then actuator is seized, if yes then....? Not much else it could be, assuming the downpipe is factory, maybe someone stuck something in the wastegate ports for more boost
