WiFi relay not appearing in AP list for initial setup

I have a WiFi relay board (single relay version) I purchased last year and for several reasons I can make use of it only now. I connected mains on the screw terminals, the blue led is lit but I cannot access it through its built-in WiFi AP. It’s not appearing in the available list of APs. I tried from my smartphone and also from a USB WiFi stick in my desktop PC to no avail (both work fine on WiFi).

Please help, how can I further diagnose this? Should I try to connect to it via the serial pins?

Well, consider it solved. I power cycled the device a few times, the blue led came in flashing and I could finish the initial setup and was able to update the firmware to the krack-fixed version.