At the moment it is very grey and raining quite a bit here. My system is showing 0w PV all day so far, I don't think I've ever seen that before during day light hours?
0w PV during the day
C
K
Short strings?
C
T
C

There is a required startup voltage on at least one string before the inverter can start generating, Gen1 = 120 Vdc and Gen2 = 150 Vdc.
If you do not have many panels on a string then they need a higher insolation level to reach the required startup voltage in order to wake up the inverter.
Each solar panel generates around 30 to 40 Volts and are wired in series on the string in order to obtain the required voltage for the inverter (much like multiple 1.5 Volt batteries to get a 3.0V or 6.0V supply).
More panels on a string means a higher voltage for the same insolation level.