Hired an HVAC Contractor to install furnace. He started and never completed install - I loss tenant who was supposed to move in as a result. Can I sue

You can certainly sue for breach of contract and recover the amount you have to pay someone else to get the work completed, but it is not certain tha tyou would be able to recover anything for the lsot tenant as these damages are not direct but consequential, i.e. damages that owuld not necessarily flow from the breach in every situation but did flow from the breach here.  It is difficult to recover consequential damages.  Many contracts specifically prohibit.  Assuming that yours did not, your right to recovery them is likely going to depend on whether the contractor knew that its failure to perform the services contracted for would lose you the tenant.