Under Add-ons menu, select Goal Seek, Open. Sending feedback? Please share and link the spreadsheet with the issue so we can debug it. Include your email so we can respond. If the Run button is disabled, you can always hit Interrupt! to enable it (and stop any previously running optimizations). To use in other docs, under Add-ons select Manage add-ons. For Goal Seek select Manage and Use in this document.