MASTIC APPLICATION CERAMIC TILE OVER DADE COUNTY HARD SEASONED PINE?

HAVE A CABIN OF SORTS IT HAS ROUGH SAW CEDER SIDING OVER BLOCK AND THE WINDOWS ARE FRAMED WITH 2 X 4S ROUGH CUT THE SILLS OUT SIDE ARE PINE AND HARD TO CLEAN I HAVE SPRUCED IT UP AND NOW AM PUTTING A CERAMIC TILE OVER THE [INE SILLS AND THE MASTIC IS NOT SETTING UP IT HAS BEEN 49 HRS SO FAR ???