The inference that manual trim was not available may not be correct, in fact the report refers to "manual electric trim" meaning the control column trim switches, this is in fact the "main electric trim", as distinct from manual trim. It is possible that the FO misunderstood the Captain's request for manual trim and attempted to trim by using the control column trim switches which not surprisingly did not work due to the operation of the cut out.
I think it is possible that the FO may have tried to use the control column switches at the Captain's request rather than winding the trim wheel due to the stress of the moment, even though he had only just selected the cut out. The FO's statement at 05:41:54 that "it is not working" would appear to me that the control column trim switch was not working, whereas if the manual wheel was jammed I'm sure he would have said something along the lines of "I can't move it" or "it is jammed".
I base this on my experience on the NG, where I have heard pilots and instructors both in simulator training and normal operations referring to trimming "manually" meaning manual operation of the electric trim switches, I've never seen anyone actually manually rotating the manual trim wheel in the aircraft during flight.