There are many possibilities...
If your fish are unable to produce a slime coating, you can try raising the fish artificially, which is really a pain, but is effective.
Pigeon strains often have trouble with fry attaching, since they cannot turn dark as other strains do. The fry are attracted to the dark object, and will ultimately attach to it. Try maybe painting the tank white, as that will make the parents stand out more.
Another trick is to lower the water level when they go freeswimming, as less water=less dead space for the fry to go in and possibly get lost.
I know it is frustrating, just hang in there. They should get it eventually.
Question:
Do they eat them when they are wigglers or when they go freeswimming and attach?
Also an update on my fry. Parents had freeswimmers for 6 days, and they were getting to be pretty big.I had about 20 wigglers attached. For some reason though, they were eaten. Guess the 7th time is the charm.
I do have some pictures, and will upload them later.
Looking like they will lay again, so keep your hopes up.
Thanks
Daniel