Why does no reaction occur for this double-displacement reaction

KNO3+Na3PO4 has no reaction and I am confused as to why this is

You do not see a reaction happening because sodium and potassium have very similar properties.

Both solutions are clear. If they switched partners they still would be clear.
Both are soluble as are the new compounds.

Actually all ions would be in the mixed solution, Na+, K+, NO3-, PO4^-3

Sorry, it does not occur because a reactant is insoluble meaning it is a precipitate, and it's KNO3.