I've unpacked my RB750, and I've seen it with winbox. All was fine.

A few minutes later, i've reset it:
- I've put a piece of wood on reset hole,
- I've powered of the routeur,
- I've powered on the routeur,
- I've waited all the leds to stop,
- I've put off the piece of wood out off the reset hole.

Now, I don't see my RB750 with winbox.

With wireshak, I see traffic on port num 1 (dhcp request) and on port 5 (CISCO Discovery Protocol).

How to see my router with winbox (or with an other tool) ?

Thanks for all.

Which port are you plugged into? It might have the default config now and you will need to be in port 2-4 because port 1 is blocked by the firewall.

I've plugged:
- port 1: I've seen, with Wireshark, DHCP request from RB750 (to ISP in real life, to my test network for me). After, it was possible to ping this port, but nothing else (a firewall on thgis port I presume),
- port 5: with wireshark: CISCO Discovery Protocol, but nothing else).
- on other port, I don't remember. Sorry.

I've opened the box, don't see anything queer. I've closed the box. And now, It works:
- I've seen the window that permit to erase the configuration,
- and now the RB750 work fine.

I don't know what has happened.

I've tested to erase configuration. All is fine. Now, with winbox.exe and the MAC address, I'm able to connect to the router.

Thanks for all.