Landcress

Hello, only just joined, seems a really good site.  Is anyone else having trouble germinating Landcress ?  I've tried sowing direct, in modules outside, modules in the greenhouse and even,out of desperation,in the propagater, all to no avail.  I shall really miss it in winter salads if I can't get it going.  The seeds are within use by date and are from 3 different packets.

For ages I was pulling it out as a weed, until somebody told me what it was. Now  I know it it useful it seems to have stopped seeding itself all over the place.