The ISScript.msi file is not a "one size fits all" download; different software requires different engine versions (e.g., version 7, 8, 9, 10.5, or 11).
Download the version corresponding to your software's requirements. Open the downloaded folder and double-click isscript.msi Follow the wizard prompts to "Accept" the license and click isscriptmsi new download
"It’s the dependency chain," Sarah, the lead architect, said, slumping into the chair next to him. She held a lukewarm cup of coffee like it was a lifeline. "The main installer throws an error at 92% every time. It’s looking for a specific script handler. The registry keys are a mess." The ISScript