Your settings look fine.
If it has started at 100%, pulled out 300Ah and recharged 300Ah then of course it will read 100% again, this is how it works, by counting energy in and out. The synchronisation settings are to make it go to 100% if the battery gets full when it is displaying say 90%. You need to ignore the SOC for the moment and carry out a full charge right through absorption to float then the 100% will be correct. Batteries often arrive at 40-50% so the initial SOC is wrong. You need that absolutely full charge to float to get everything aligned.
The other explanation is incorrect wiring of the shunt. See