Hello
.dsb is the model file format which can be opened only in the DesignBuilder application.
.eso, .epw, .htm, .drs and .drb are the results file format which can be opened in the Results Viewer application.
I understand that you want to open some result files from Simulation Manager by opening Results Viewer.
We are using the default Windows operating system settings. So this has to be set at the Windows settings level and not at the DesignBuilder settings level.
This can be fixed by assigning the default application for these file formats. Save files (.eso, .drs etc.) somewhere on your desktop. Use mouse to right-click the file and select the open-with option and choose the Results Viewer as the default application. Repeat this process for other file formats. After making these changes, please restart the DesignBuilder application and try selecting the same button in Simulation Manager. Now the Results Viewer should open the results.