But the Starting material spots show the same too. I was already tried to TLC the starting material with KMnO4 staining before, and it just showed 1 spot. Could the problem come from the mobile phase?
What if the problem is come from my product, what should I do? Should I synthesis it again?
Some of the reactants such as same as a reactant so one of the spot is reactant and another one is product ( in that case you may put reaction for some more time)
You have not written what is your starting material. Initially it was giving single spot. Is it stable or decomposes with time? Are there positional isomers?