In general people are very visual, and staging does help a lot to get across an attractive picture to buyers of how their future home may look and how they may want to decorate the apartment after they buy it. Virtual staging could be a good idea too - it makes on-line pictures look great!
To decide whether your apartment needs to be staged or not, one would have to know your apartment better, if it is furnished or empty, if it is cluttered, if any cosmetic renovations (quick and inexpensive) may make it look more fresh and desirable.
It would be useful to analyse feedback your agent have received from people who visited your apartment during these 6 month - what were they saying, what impression it makes without a staging and what impression you would like to achieve?
Sometimes, having some nice artistic objects around, paintings, flowers, some bright tasteful and happy color accents (like a nice table cloths, a big vase, or an accent rug) can change a way a space feels by setting up a brighter mood.