The old Goal Seek (written by a third party?) used to work fine (slow, but it got a result). It has disappeared and appears to have been replaced by this new Google Goal Seek that doesn't come up with a result. My goal is complex and does not correlate linearly with the cell being changed. It also removes the formatting of the cells being changed and overwrites the formula in the goal sell. Really annoying! Give me back the old one! Update: If that's not enough the "Send Feedback doesn't work either"

Good job. It feels a bit more familiar than the alternative add-on called Solver. It isn't exactly blazingly fast. But it works. I'll never understand why Google couldn't have built a native Goal Seek algorithm into Sheets. It's something that everyone needs and uses. And good old Regula Falsi is easy to program.

NOICE