Hello,
If you want to convert truss model to frame model, you can simply delete the "truss specification" as I suspect it was there in General > specs or in the same location you can find "moment release specifications". These commands ensure the behavior of the structure whether it will behave like frame or truss.
I am not sure as why you want to convert a truss model to frame but if the above doesn't help. I recommend you to upload your model.