I've got a CCR1036 running RouterOS version 6.7.
The NTP package was not working so I've decided to uninstall it and to utilize the NTP client only package which is within the RouterOS package.
I did that and I captured the NTP traffic from and to the router. So now I see that the router is sending NTP packets to the NTP servers, and it is receiving responses.
The problem... the clock still does not synchronize!
/system ntp client
set enabled=yes mode=unicast primary-ntp=84.54.128.8 secondary-ntp=212.70.148.16

system ntp client print
enabled: yes
mode: unicast
primary-ntp: 84.54.128.8
secondary-ntp: 212.70.148.16
poll-interval: 16s
active-server: 84.54.128.8

system clock print
time: 06:13:54
date: jan/02/1970
time-zone-name: Europe/Sofia
gmt-offset: +02:00

How can I further troubleshoot the system clock synchronization?

try some other NTP servers from pool.ntp.org

@normis: I just checked that NTP server. It is working fine. I noticed a couple users here are having trouble with NTP client and CCR with V6.7.

I assume you have seen that v6.10 is the current version? The troubles I have seen are related to NTP package, but the OP says he uses SNTP

Same issue on 1100ahx2. Disable and enable make it resync, or reboot. The weird thing about disabling is if you do it via console/script it doesn't work, do it via winbox and it does.

try some other NTP servers from pool.ntp.org

@normis
I did that. I configured other servers from 3.bg.pool.ntp.org. It's still the same:
sys ntp client print
enabled: yes
mode: unicast
primary-ntp: 193.104.79.174
secondary-ntp: 46.47.81.47
poll-interval: 16s
active-server: 46.47.81.47

system clock print
time: 10:37:37
date: jan/08/1970
time-zone-name: Europe/Sofia
gmt-offset: +02:00

Still the local clock does not synchronized. Packets are sent to the NTP servers and received:

tool sniffer quick interface=ether3 port=ntp
INTERFACE TIME NUM DI SRC-MAC DST-MAC VLAN SRC-ADDRESS
ether3 15.594 1 -> D4:CA:6D:73:A1:06 00:30:48:8D:3E:EF 217.10.251.66:123 (ntp)
ether3 15.598 2 <- 00:30:48:8D:3E:EF D4:CA:6D:73:A1:06 193.104.79.174:123 (ntp)
ether3 47.589 3 -> D4:CA:6D:73:A1:06 00:30:48:8D:3E:EF 217.10.251.66:123 (ntp)
ether3 47.594 4 <- 00:30:48:8D:3E:EF D4:CA:6D:73:A1:06 46.47.81.47:123 (ntp)
ether3 79.6 5 -> D4:CA:6D:73:A1:06 00:30:48:8D:3E:EF 217.10.251.66:123 (ntp)
ether3 79.605 6 <- 00:30:48:8D:3E:EF D4:CA:6D:73:A1:06 193.104.79.174:123 (ntp)

I'm a bit confused...

Same problem here
NTP is not working in 6.10