I would say after a week or 2, if you have no signs of seed growth, ditch them and start again...

The whole idea of scratching the seeds is to emulate conditions in the seeds natural environment.

Its almost like a fail safe...

Some seeds wont actualy open untill they are subjected to a certain temperature / condition.

Try taking to them with a tiny bit of heat, or rub them on glass paper to take off a few layers of the outer shell.

::M1557::