There are a few reasons why a tooth will not move, obviously ankylosis is one of them but the percentage of ankylosed teeth is not very high. The second reason is the lack of space opening, the space should be opened wide enough i.e. more than the contra-lateral tooth to avoid any contact or friction on the adjacent roots during traction...has this been done in a sufficient amount, if not you may encounter the situation you have now. I would suggest you open the space with excess if this is not the case. The third reason is leaving a bony bridge in the direction of the traction that may make the movement harder or impossible.
We should always evaluate the space and if in doubt, open it more. If the impacted tooth is very close to the roots of adjacent teeth, it is a good idea to try first a traction on the impacted cuspid in another direction to pull the tooth away from the proximity of the lateral and bicuspid. This can be done by pulling on the tooth with anchorage from the contra-lateral side like the molar on the other side with an elastic chain, you can anchor the molar with a TPB if if you do not have bands on the molar a bonded TPB could do the job. If you are experienced with TADs, a TAD can also be inserted near the mid palatal suture and used as anchor. You will see if the tooth wants to move in a direction where there is no restriction. If it does there is no ankylosis and after the space is opened with excess you will be able to use a mouse trap or a Kilroy spring to extrude the cuspid in a vertical direction and after pull it on the buccal side.