The data bar option isn't available for conditional formatting on a table. The only options are background color, font color, and icons. I have them working on another visual (matrix). Is this option not available on the table visual?
Seeing the same issue w/ a field formatted as a whole number w/ a "Sum" aggregation/ summarization. Databars options is not available. The range between the min and max value is <1%. Wondering if BI is trying to be smart here and urging me not to use data bars
Data bars formatting is available for numerical values only and not for any text values. Ensure that the data type of the field (or measure) that you need data bars for, is numerical.
I had the same issue and figured out even with numeric column you need to have an aggregation function on it to be able to use Data Bars as conditional formater. I couldn't find out the reason, but if you use an aggregation then format the field with the data bars, then get back to Don't Summarize, you still have those data bars with the raw column values.