Wow. Time flies. The thread below start in 2021. Anyway, the main thread I remember seeing before is here: Estimated flight time not visible anymore when planning a flight
There were a few more recent threads but without much support (votes) and were very short. I didn’t really see any universal fixes for the issue. However, you might try using an IFR flight plan and see if it shows up. That might narrow the issue. Hope it sorts itself out for you.
Regards