Will frozen shoulder heal after a year and a half?

Possibly: Frozen shoulder is a difficult entity, often we dont know why it occurs and then often can't say how long it will take to resolve. Can definitely take a very long time for the motion to return and sometimes it doesnt. Hard to say if it will "thaw" at this point if you have had it over 18months. May be worth seeing a surgeon for possible capsular release if your range of motion is very limited.