The message means that one or more cells used by the regression looks like a number, but is not considered a number by Excel.
A quick look at the screen cap, there is no obvious bad data. The obvious clue is that a number is aligned on the left side of the cell.
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My next guess is the numbers under "Predicted Monthly".
is 1200 in a cell separate from "A models", etc? The look like the values are all in one cell. If you use that as input to the regression, that would cause the error.
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The "easy" way I know of to find text values mixed in numbers is to import the data into PowerQuery. You will instantly see which cells a text, ie
A less easy way is using the =IsText() function, ie