According to VICSIG, it is "under repairs", however it has kept that status for over 2 years!! The last reference online regarding that unit was a truck crash back in June 2018, but hasn't appeared since. Has it been withdrawn perhaps? Or is it being tested for D2 refurbishing (they are at refurb age)?
Vicsig can be slow to update, depending on who has taken responsibility for that section/page. Have a look at the V'locity page; it hasn't been updated for nearly two years now and I know there are Vlo's in service that are still listed as under construction and others shown as being in Vline livery which are now in PTV livery. The N class carriages pages has also suffered from a lack of updates for quite a while now. On the other hand the E2 page is quite well maintained but if the same person does the D2 page I don't know.
You might find that 5017 is in service by searching the photos section on Vicsig and/or Marcus Wong's site as two places I know of to look at