The ability to deduct mortgage interest is more restricted for 2018. Any portion of a mortgage used for something other than the home is not allowed to be deducted, plus there are limits to how much of a mortgage that interest can be deducted on.
But, if you being told that none of your interest can be deducted, go back through the entry screens and be sure that you mark the question as to whether the mortgage is secured by a property is marked YES. As if the mortgage is not secured by the property, then it is not deductible. See the sample screenshot below.
Plus see more information below:
https://ttlc.intuit.com/replies/3300473