Presuming you paper filed the 2016, Christmas might be a good estimate on that refund.

I E-filed 2017 & 2018 returns on 5/5/2020 and both clients just received the refunds this week.

As mentioned, the Practitioner Priority Hotline is the only way, I know of, to find out the status of 2018 and prior returns. 866-860-4259