Faezeh Ladani
Ansys Employee

Hi Balaji, 

It looks like to be a very old version of HFSS. What is the oldest release of AEDT you have? You can try opening it in that version. Save and try to open it in newer builds in a couple of intervals.. Let's say you were able to open the file in 20R2 and now trying to open it in 23R2... If that gives any error message, try Purge History in 20R2 file. Save it and then open in 23R2. 

To do Purge History, simply select all objects. From menu>Modeler>Purge History.. Then save.