CCGX on-screen display contains an indicator of the form "ESS#x" (for various values of x)

e.g. "ESS#1" or "ESS#4" or even multiple items, e.g. "ESS#3#4" or similar:

This is not a fault indication!

It is simply diagnostic status information.

The Victron ESS system, running in Distributed Voltage and Current Control (DVCC) mode, is just indicating that it is in specific operating states that are typically related to the startup of a ZCell system or just indicating it is operating below the 'minimum target SoC'. 

Here is the list of what these numeric codes mean:

• #1: SoC is low (below the configured target value of "Min SoC" in the ESS menu)
• #2: BatteryLife is active (See Victron online ESS manual)
• #3: BMS disabled charging (ZCell BMS is commanding a zero charge rate)
• #4: BMS disabled discharge (ZCell BMS is commanding a zero discharge rate)
• #5: Slow Charge in progress (part of BatteryLife, see Victron online ESS manual)