HMC767LP6CE unlock problem

We config the HMC767 register like this:

REG 1 2
REG 2 1
REG 5 50F1CD
REG 6 1D3F
REG 7 304865
REG 8 16FFF
REG 9 3264
REG B 1E061
REG E 1
REG F 81
REG 3 AB

the REFCLK is 50MHZ, we want to get the 8.55GHZ signal output,  but the PLL not locked.

I need your advice , thank you!