If it isn't stock, the tune may be inhibiting write, in which case you need to use bootmode to overwrite it.
If it has a riser (you have to open the ecu to find out) you'll need to replace the riser with a stock flash. If you don't have the equipment or skills to do so, you'll need an entirely new ECU.
I also have a stock ecu, and I've tried the same thing. and I'm just trying to datalog at this point.