Odd one. Since adding a fridge and freezer to my system, it will only work if the setting in the multi is changed from 'on' to 'generator only' either using the switch or software. In the on setting, it tries to synch, lots of clicking, but no link. Eventually the multi turns itself off. Solar seems unaffected. Have tried many different input current limits, doesn't help.
Setup
EasySolar II 5K, onboard GX disabled
4 x Pylontech US5000
Cerbo GX
Hyundai DHY8000SELR-T, using single phase 230V output with earth/neutral bonded. Output is stable at 229V.