Dale,
I would suggest heating the soft stuff up to see if you can kick off the reaction that makes it set, but it sounds like it's quite warm where you are. You could play a hot-air gun over one bit until it's still just touch-bearable - you will then need to leave it alone to cool down before you know if it's worked.
You certainly want to leave it a day before you do anything rash - it may set if left to itself overnight.
As to why, is the second application wafer-thin? It sounds like you're making slow mixes (I'm with vairman, I mix mine so it goes off in 10-15 mins) so they take some time to build up the heat to make the setting reaction happen. If your second application is very thin, it may not be able to generate enough heat to go off (big surface area, but small volume) - though with air temps in the 80s, I doubt it.
Andrew