IP Camera NTP not working. Is my NTP server working?

Not sure where I could try to ask people who might have experience with this but I thought I should give it a try here.

Been trying to sync my ip cameras' time to my NTP server for some time now but every time I checked the NTP checkbox for my cameras, it becomes unchecked after some minutes and the time drifted again.

I am quite sure I had setup my NTP server correctly (I am using an Ubuntu server to act as a NTP server). I followed videos and explanation to setup the NTP server (Think this page summarizes it https://www.howtoforge.com/tutorial/ubuntu-ntp-server/ ) and verified that I could get the intended outcome from the client side by using another computer in the network. The udp port 123 and firewall are open for NTP within the network as well. I could ping to the NTP pool from my NTP server using the 'ntpdate -u ' command and doing a 'ntpq -c lpeer' does return a record among them with the * indicator that it is taking its time from the internet. The status of NTP is also active(running).

At this point, is it safe to conclude that the NTP server is working as intended and my issue with my camera lies elsewhere? Or is there something else that I might have overlooked? I am quite new to the whole NTP thing.

Thanks.

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