Hello Fernando,
Here are 4 of the most common ways to reset an AP:
1 - Console into the and use the reset/FactoryDefault credentials
2 - If possible SSH into the AP and delete the startup config
3 - Use the discovery tool with reset. Reboot AP prior to using the tool
4 - Adopt it onto a controller and have it pull the new config and credentials
If all else fails, please contact GTAC for further assistance:
How to contact Extreme Networks Global Technical Assistance Center (GTAC)
I would recommend you segregate this AP from the rest of the network first, then attempt whichever option works for you.
Can you log into any other AP?
Do you have a controller or virtual controller you can access?
There are other ways of accessing the AP and resetting it from another AP or controller, but we still have to have the bare minimum to work with.
Regards,
Chris
Christoph S.