Regarding USB port please make sure that you have not connected usb stick to port with mark 1:1. Other 3x USB ports are correct for updates and reading usb stick.

Regarding synchronization and Master - Master (M-M) status on both ECDIS units:

Please check proper connection and LAN cable condition on both ECDIS monitors.

It can be found on the bottom of screen and should be properly connected to LAN#1 port on both units. 

If you have done any corrections on the LAN ports, please reboot both units according to Switch OFF and switch ON procedure.

a. shutdown both station (Sailing Mode > Settings > Exit Navigation Mode > Shutdown)

 - Master ECDIS first

 - Backup ECDIS afterwards

b. start Master ECDIS first, let it fully load to Navigation Mode

c. start Backup ECDIS, let it load to Navigation Mode

d. Check M and B logo on the lower left corner of the screen for the Master and Backup station respectively. 

Please inform us about results.

If above did not gave a positive outcome, than we will provide you next steps to solve synchronization problem.

Furthermore please go to SERVICE SETUP (password admincw) and than to NETWORK tab.

Please make pictures of the above mentioned on both of your units. Please do not change anything on your own.

This will help me to advise next steps to you.