Hard to tell from the picture without a side view but it appears that you have excessive wing to float decaledge which makes it difficult to actually get on the step. In other works you only need two to four degrees positive wing incidence to the float top decks.

Another factor that is not visable is the CG to float step relationship on that airplane the aircraft CG with the floats should be up to but no more than 3/8ths inch in Front of the step, never put the CG behind the step.

Either one or a combination of both is the problem.

Johhn