When multiple versions of STAAD.Pro are installed on the same system, the most recently installed version is invoked by default, even if the input file was created using an earlier / later version.
Therefore, it is recommended to explicitly specify the required STAAD.Pro version when opening the file, using the “Open With” option like AutoCAD.
When multiple versions of STAAD.Pro are installed on the same system, the application automatically defaults to launching the most recently installed version. This behavior may result in users unintentionally opening a version different from the one required for their project. It is recommended that Bentley consider providing a configurable option or built‑in mechanism that allows users or administrators to explicitly select the preferred default version. Such a feature would greatly enhance usability and help avoid version related inconsistencies.