Hello there - your seeds are fresh? You say this years lot?
I soak my seeds over night - then plant out each seed into a peat pot individually- with potting mix soil. I have never "nicked" gourd seeds - the only seeds I have ever nicked are cycad seeds.
Keep the soil moist - but never WET - and leave in a warm sunny spot to germinate - I would think after three weeks of waiting - the seeds may not germinate at all. My germinating seeds are pretty much up and running within 10 - 14 days at the most. I doubt if its the varieties you are growing - sounds more like seeds that are not mature and fresh - although I have retrieved seeds from gourds made into musical instruments that are years old - they do take much longer and never 100% success rate - but enough to get plants to full growth and producing fine gourds. If you can bear the sacrifice of one of your slow germinating seeds - squeeze it hard between your fingers - if it oozes out sloshy "matter" you know the seed has rotted and no longer any good - or if the seed collapses then it too is not any good and is immature.
Cheers.