Tacye is correct that your levers need regulating by a harp technician. The symptoms you describe are very commonly experienced as a harp ages, especially in fairly new harps during the first year or so.
Being out-of-tune is very frustrating, but you can temporarily work around it by setting the levers for the tune you want to play. First tune all the strings that are in the open position (i.e., the levers are all down). Next pluck a string with the lever up and listen. Lower the lever and adjust the string with your tuning key up or down, as necessary. Raise the lever, pluck and listen again. Repeat this process until the string sounds in tune with the lever up.
Never tune the string with the lever up. The strings may catch and not slide properly (and hence not change pitch) and it is very hard (damaging) on strings to tune them when they are engaged by the lever.
Hope this helps and you can find a regulator soon, or you can buy Dave Kolacny’s book and figure out how to adjust the levers yourself.
Best wishes,