not sure, I've never had an issue with livebearers NOT breeding, is there anything else in the tank with them? I keep guppies 1m-3f and it seems to keep the males from stressing the females too much, although I've noticed that if one female is considerably larger than the others, the males will go after her 90% of the time.
Since the females can store sperm for months at a time, and have multiple batches of fry with that stored sperm, odds are usually that they are already pregnant if you've purchased them recently. So if we start with that idea then maybe they are stressed. What kind of diet are you feeding them? What are the water parameters like? Given that they had to acclimate to a new environment it may have stalled them on the breeding process.
I've kept guppies in 8.0-8.6 PH before and they acclimated fine, but did not reproduce at all for the few months they were in it.
Endlers and guppies can interbreed also, so be ready for that possibility.