Blue Sea 8247 Multimeter Help

[GuyO]

Hi, Although I have been a member of this forum for a few years, this is the first time that I have reached the point where I have to reach out for help.
I have 2 Blue Sea 8247 Multimeters installed onboard. One unit is for monitoring the generator and shore power, which works great. The second one is for the 220Vac generated from the twin Victron Multiplus 3000/70/24 Charger inverters. And, up until recently, this was working fine too. It had been for the past umpteen years, circa 2005!
The symptom is that the display has four indicator LEDs for indicating what the digital display is showing. Voltage, Current, Power and Frequency. At present the Digital display is blank and all four LEDs are flashing in unison. Nothing has changed concerning the vessel so I am wondering if anyone out there has any idea of what the problem could be? All connections are tight and good. The coils appear to be ok. The fuse is working and correct.
If anyone can provide some guidance or insight I would be very grateful.
The boat is a 70ft ocean-going custom-built steel cruiser. Currently, we are plugged into shore power and I disconnected shore power and ran on purely house batteries and no change so now I am stuck. If anyone has had experience with these excellent meters I would appreciate advice/guidance.

Kind regards
Guy