PTP 600 Power Transmit

I have been configure the Cambium PTP 600 with radiowaves sectoral dual polarized 16 dB and facing radiwaves parabolic antenna single polarized 34.6 dB (1,2 m)
The maximum power transmit that can be configure only 12 dB, and still cannot got the signal. The distance of this link from shore to fso vessel is almost 22 km and we need more bigger power transmit for that distance.

We tried already to update the license key to zone 4, but still cannot get power transmit more than 12 dB. If you have any solution for this situation, please let me know. All your response is very appreciate.

Thank you.