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 ...

There are two ways to fix this cause of the #SPILL! error. First, select the entire spill range (or at least the cell or cells causing the blockage), and drag it to another area in the worksheet. On ...