Problem solved. Initially I tried to reset it like in manual, power up, press reset for 10 seconds, wait 5 minutes. That didn't work for me twice so what I did was

- power up
- wait 10 minutes
- press reset button for 15 seconds
- wait another 5-10 minutes
- Works afterwards.

Don't know, maybe earlier I pressed it for too short, or pressed reset incorrectly, but all in all after 3rd, longer attempt  factory reset occured and static ip setting reversed to DHCP.