Table won't edit

I’ve done this successfully before many times, but in my current project when I set editingEnabled to true, the DataSource for the table never fires the RowIsEditable method. Nothing happens.

I’m positive I’ve done something stupid.
Can anyone suggest likely culprits?

Did you implement the datasource required interfaces?
You might have just copy pasted the methods from another project or datasource and Xojo never calls the appropriate methods because the interface is missing.