currently all harps do not allow /use when kept in the ranged slot (2h is fine), unless the 1h or 2h weapon is selected as primary. Under investigation.
basically harps cannot be /use in the ranged slot .... if the harp is in the 2h slot it works fine ... changing harps from 2h to ranged and vice versa has no effect on this ... bows work fine for /use in the ranged slot ... harps CAN have their /use fire if the player is holding 1h/sh, 2h/sh weapon, the /use fires and then the ranged harp is selected