I was trying to configure this device and after many different fail configurations and hard resets it stopped showing up as an available wireless network.
Hard resets don't fix the problem. I press res/wps button I turn on the device and keep pressing until led is flashing, then I release the button, but nothing.
It was working fine until I powered on a Mikrotik hAP ac3 in order to do some configurations also in it. I'm just stating facts, I'm not assuming that this caused the problem.
Any suggestions?

Looks like you used the correct procedure: https://wiki.mikrotik.com/wiki/Manual:Reset

Should work, unless somebody has set routerboot-protection-mode : viewtopic.php?t=181158
(1 second blinking of the LED.)

You could not get in through ether2 , with WinBox? (Neighbor discover, MAC address connect)

Some USB console adapter or "Woobm-USB" MT stick to connect?

Next step would be "Netinstall", what has very strict requirements to execute.

Looks like you used the correct procedure: https://wiki.mikrotik.com/wiki/Manual:Reset

Should work, unless somebody has set routerboot-protection-mode : viewtopic.php?t=181158
(1 second blinking of the LED.)

You could not get in through ether2 , with WinBox? (Neighbor discover, MAC address connect)

Some USB console adapter or "Woobm-USB" MT stick to connect?

Next step would be "Netinstall", what has very strict requirements to execute.

When I press res/wps and power on the device the usr led which is off, just turns on. I suppose that's not considered as 1 sec flashing, right?
I can't get through ether2 (winbox). I change the IP address of my NIC to 192.168.88.2, I connect my PC to the device but when is trying to connect it fails.
I have no usb console adapter.
I suppose netinstall is my only choice now?

EDIT: I managed to connect with winbox via Neighbors as you said. I "reset all configuration" and now it's fixed. Thank you very much!