@Bruno_Alvarenga Sorry to hear about the sudden problems. No fun. You used it before with no issues? Was there something different that happened before it stopped working? I’m not official RICOH support, but maybe I (or someone from the community here) can help.
You said it stopped working and the power button doesn’t work. Does that mean it does not start up? It does not boot up at all? No LED lights?
One possibility is that it has no charge. THETAs can be “picky” about what it will charge with. Ricoh recommends that you only use the one supplied with your camera. A poorly made cable could cause a voltage drop which will bring the charger delivered output voltage down below what is expectable for charging the camera. Have you tried plugging your THETA into a wall socket, not a computer? (Use a USB adaptor.)
If it appears like it really just stopped working and has some mechanical problem, official RICOH support may be your best choice:
If you’re in the US: https://support.theta360.com/en/contact/
Outside of the US: https://us.ricoh-imaging.com/contact-ricoh-imaging/