I see that there is a big difference in annealing temperature between your primers. Did you design these primers yourself, or did someone do it for you? And have you considered changing one of the primers to reduce the difference in temperatures?

You could also try reducing the primer annealing temperature by one or 2° from the lowest (to 62-61 °C). Of course, this will worsen the specificity of the reaction, but see if it helps you get at least some results.

you can also try playing with the denaturation temperature and elongation time in your protocol

To fix low-Tm primer issues in PCR

try a touchdown PCR and use DMSO at 5% max

next time, just design primers with Tm difference under 2°c

fred