Over 4 weeks and still nothing...sounds like immature or infertile seeds, but unless the use of your warmer has given consistent results in the past it may be too warm. Room temperature such as placed on a counter-top should be adequate to sprout most seeds. Also, continuously being very wet may cause mold spores to colonize on the seeds. Mold can be difficult to see with the naked eye until it has basically taken-over the subject. Have you tried just soaking them for 6-8 hours, then draining with a towel/cheesecloth (do not pat dry) and holding in a small glass or plastic container, not covered tightly to allow it to breath, and keeping on the counter-top? It can be a dark location, or in a container that does not allow light transmission, as sunlight is not required for sprouting.
I haven't done any sprouting for a very long time (haven't been that interested in it) but have recently been studying seed sprouts as a food source, and it seems that the universal recommendations are to soak, drain, allow them to breath and always keep at room temp. Harder or larger seeds take longer soak times and many seeds may do much better with a rinse/drain once daily or more often. The repeated rinse/drain aids in re-hydration and helps remove mold spores that may have accumulated on the seeds. It's a double-edged sword when sprouting...you need moisture to wake-up the seeds and mold thrives in moist environments, so with rinsing you are reducing the population of mold spores on the seeds, hopefully enough to prevent it from colonizing and propagating.
Just some thoughts...not saying the methods I mentioned are 100% the best way, or that what you're doing is all-out wrong, only that maybe a few changes in your process will get those reaper seeds going with consistent results.
Anyone else have some ideas or proven methods?
Eric