Astrantia seeds first need a warm period for about 4-6 weeks and after that a cold period, so you need to sow them as soon as they are ripe.
For now: put them in the fridge after temperatures has been warm enough to have them 4 weeks around 18°C. Leave them in the fridge for 6 weeks. Check them so now and than, because they start to germinate at 5-12°C.
Are you sure you had thick viable seeds? 'Ruby wedding' is a cultivar, so the seeds may be sterile.
I received these seeds from another DG member, who told me they were easy to grow from seed and he sows in the fall and they sprout in the spring. That's why I winter sowed them. Don't think I have room in the fridge for the whole milk gallon! Will see if I have more seeds to experiment with. Thanks for the info.
I also have some "Ruby Wedding" seeds that have been sitting there for more than a year. I have decided to wait another year before chucking them into the garden, because this past month (late winter) some of the other astrantia seeds (no name, only color of flowers) I had in pots for ages, germinated. Will let you know if anything happens with the "Ruby Weddings"