I also am having some problems. I wrote to the postal service and they replied with sort of a cut and paste reply, But I got an answer, I have deleted it so i cant copy exactly what they said, Something like this. We apologise however some countries had stopped receiving international mail from certain locations due to Covid restrictions. They also wrote we understand it can be very frustrating but as you had mentioned yourself that Cambodia has numerous arrivals and departures through their capital airport daily we hope they will resume normal services soon! lets hope they get back to normal soon

Same problem here, although I'm out in the province which complicates stuff.

Local postoffice ensured me everything is working fine. They also told me mail to this province (RTK) is sent out every 7-14 days from Phnom Penh because there's hardly any.
He didn't convince me. Went with DHL because I really need that shipment.

I checked with the post office in Siem Reap as I was planning a shipment from India. He assured me that deliveries from India are normal and the current transit time is around 7 days. I shipped last week and according to the tracking the parcel has been sitting in Bombay for 4 days. It could be that India are lax in updating the database. Another 2 days to discover if it arrives in 7 days. I think its not always Cambodia Post who is to blame

Further to my previous post I found from a different tracking app that my parcel already arrived in Phnom Penh even though the EMS tracking shows it is still in Bombay.

I highly recommend the website 17Track.net for anyone wanting to track a parcel as it seems more up-to-date even than the EMS International website.

For the record the package from India did indeed arrive in 7 days as the post office promised. Highly recommend EMS service.