We found the problem issue that I used Revit 2021 but I did install the program but it will pop-up as attachment file
Hi @arch.wuttisak,
This typically happens when Revit is not installed in the default installation directory. Can you check to see whether that is the case?
Sefaira will look for the default directory for Revit and if it cannot find it there, then it will not work, unfortunately.
Kind regards,
Niraj