ESS does not feed to grid

Hi
Couldn’t find a solution in th database yet…
My 3 phase Multiplus II 5kW with MPPT 450/200 was working fine since 6 months but now found out, that I don’t feed the grid when generating more than I need. This was working until last month. Now I updated the ESS Assistant and the Cerbo. Distributed the updated ESS settings to all 3 inverters and rebooted the cerbo multiple times. My MPPT starts producing right after reboot but then switches to -15W (idle) mode without delivering the grid. Any idea?