If you did indeed secure your device (flash protection with mass erased), then you cannot unsecure it (as it would be against that concept).
See https://mcuoneclipse.com/2012/11/04/how-not-to-secure-my-microcontroller/ what securing means. Basically the debug probe tries to read from the device but fails and it returns the memory area as secured.
There is a small chance that it is a user error and your device is not secured (see https://mcuoneclipse.com/2012/05/28/device-is-secure/ ) so can you check that indeed you are using the correct device and connection.
Any indication what you did before? Indeed if you programmed a wrong binary with the wrong security bits, then your device is 'bricked' and you need to replace it.
I hope this helps,
Erich
After clicking several times in the Try unsecure anyways, this window opens
@Rafa_Mondragon did you manage to find the solution? I am stuck with the same lock device problem and same message is being displayed once I try to flash the device.