Can you post a photo of him? Do you "play" with the seeds to get him interested. Pick them up and drop them again, push them around with your fingers. He will copy what your fingers are doing. An alternative will be to handfeed him defrosted peas. A 4 week old baby needs about 90 peas per day divided into 3 meals of 30 each. One usually handfeed for a day or 2 and then they start eating the peas by themselves. Then one can start adding small seeds.