Incoming port 123 connection refused

I am allowing certain incoming ports and forwarding to an internal server IP.

However despite allowing and forwarding 123 in both UDP and TCP, its being blocked by the router.

I know you can install the NTP server, but I already have a GPS locked NTP server on my LAN which the router takes time from.

But I want my external servers to use my NTP server. Everything else I forward works like a charm. I think its some internal block as you can install the NTP server on the router.

Thanks!