The WLS and Forms/Reports version must match. So F/R 126.96.36.199 must be paired with WLS Infrastructure 188.8.131.52.
if you have 12.1.3 then there is no Forms/Reports version that will work. As Mike said, you need to use matching versions and ther eis no 12.1.3 Forms/Reports version. Use 184.108.40.206 instead.