On December 20, 2019, attempting to patch EQ left people with an, "Error: The downloaded file is incomplete of was corrupted", error message.

As of 1 p.m. EST on December 21, it still has not been resolved.

Go here https://1drv.ms/u/s!AlGkX4lENDeSmSWs...U6ozb?e=Zy4FBw and click Download in the upper left corner. Save it in your EverQuest folder. Then start the Launcher.