It takes at least 48 hours if not longer for CYA to dissolve. Initially, your easiest route, ironically, would have been tri-chlor tabs! FC=0, pH=7.8, CYA=0? Trichlor adds FC, Acid and CYA.

HOWEVER, at this point, I'd wait and see if CYA comes up. Otherwise...it is impossible to have FC = 8, CC= 0 and TC=5. because TC = FC + CC always, by definition.