If candidate is reluctant to accept the offer 1) either he might be holding some other better offer and waiting for that confirmation 2) He might not be happy with salary offered by you 3) Current employer might have offered some hike proposal and he might be waiting for that confirmation. 4) He might not be convinced with the Designation offered.
If the candidate is really good ( as he completed 3 levels) please discuss with your Management and see if you can offer some additional amount.
Before which please talk to the candidate and find out what is in his mind. Encourage him to come out and see if you can pull him.
If not close his file and look for new candidate.
16th May 2019 From India, Madras