I also have problems with onion and garlic chive seeds. I soaked them over night and not one germinated of about 20! I have a tray of new garlic chive seeds out and I'll let you know. They do like cool weather but not cold weather - above 10Â°C, which I think is 50F. And I think they need even warmer weather for germination. They are cool-weather crops but they germinate before winter.
I did not know about leaving them open to the light but I do know that the plants like full sun (like all day) but this should not be hot. The instructions I have say 1cm below the surface.
This is a good article to read: https://anrcatalog.ucdavis.edu/pdf/8008.pdf
Not to hijack the thread but do you or anyone plant other crops with the onions? I was thinking of sprinkling mixed lettuce seeds with the baby onions and mustard with the larger ones (if they sprout). Then I pick the babies for salad as they grow too thick. I am planning on planting the garlic chives along the edge at the end of winter (as far as I can tell they die down in winter).