Try these solutions depending on your situation.
Check that the computer is connected to the network.
To monitor projectors even when they are in standby mode (when the power is off), see the following for the necessary settings for your model.
https://download2.ebz.epson.net/sec_pubs_visual/apps/epmc/settings/EN/set_standby_mode.html
When not using the Epson Projector Connected Agent software, depending on your projector, if a USB flash drive is not connected and the projector's A/V Output is set to While Projecting, the firmware cannot be updated. Connect a USB flash drive that has 200 MB or more empty space to the projector and change the A/V Output to Always On.
The firmware may be corrupted. Try updating again.
When not using the Epson Projector Connected Agent software, if you cannot update the firmware on a DHCP network, disable DHCP and try updating or copying using a fixed IP address.