The inverter detected that a PV string is connected to the DC input with reversed polarity.
CauseA PV string's plus and minus conductors are swapped at the DC input.
Recommended fixCheck the PV input polarity and reconnect the string correctly.
Source:036_BManual_SUN-3_4_5_6_7_8_9_10_12_15K-G06P3-EU-BM2_20250506_en_0eb78440.pdf· page 56