You will get an error if Flash Fill cannot find the pattern. The first thing to check is that you're using Flash Fill close to the source data (e.g., in the adjacent cell). For instance, it won't work ...

How to automatically fill increment cells in Excel using the Autofill function How to automatically fill increment cells in Excel using the formula Interestingly, we don’t even need a formula for this ...

Microsoft Excel's Formula by Example helps automate repetitive tasks in structured tables in Excel for the Web. The tool is similar to Flash Fill, though it generates dynamic formulas that update with ...