It is impossible for a lawyer to advise on a lease without reading it. That said, very often a lease will contain a prohibition against assignment or subleasing without the landlord's consent. The key is whether or not that consent can be reasonably or unreasonably withheld.
Take the lease to an attorney who specializes in this area.
As always, the key is to think outside the box. Of course your lease has to be reviewed but it is not uncommon in New York City to have a commercial lease where the landlord has the unfettered right to deny lease assignments. If you as the commercial tenant have a real buyer in hand but are being prevented from finalizing a business sale due to an unreasonable landlord with a no-assignment lease provision, you may want to consider filing for bankruptcy if you are in a precarious financial state and NEED to sell your business. You would file for bankruptcy, assume the lease as an asset, and then sell the business in context of bankruptcy. The bankruptcy court has authority to supersede the non-assignment clause in order to effectuate a sale. Timing is everything.