@ToneAU thanks, good catch! Indeed it seems port 1 failed on the old main unit. It was running fine on port 3 upstairs as satellite. Tried port 1 and now it couldn't find the main node (flashing red).

@David-TP Hi, thanks for replying. Yes, the old main is now working well upstairs. Nothing happened to the cables/connections when the problems started and everything felt securely attached still...

Hello. Setup: 2 XE75's, main+node mesh, connected to ISP via VLAN 300 (no modem in between). It's been working flawlessly for months, but yesterday suddenly no internet and a solid red light on both...