RB960PGS Netinstall recovery procedure

Is the recovery procedure with Netinstall and 1st eth port PXE boot method the same for RB960PGS (Power Box Pro model)? I have a problem with this unit after downgrade attempt. I had new unit with ROS 6.38.1 and attempted to downgrade to 6.37.1 (wanted to check SFP port will work with OEM SFP module with older ROS). After downgrade unit was no boot. Only blue PWR LED lights solid. I try to turn on power with pressed reset button and wait while PXE procedure starts but nothing happens. I tryed 1st eth port, and then others, without sucessful PXE boot with netinstall. Before downgrade unit was 100% good.

It is the same procedure. Have you tried a different PC, or adjusting Windows settings, like Firewall etc?
Is the cable directly plugged into the PC, or there is something in between?