FX30: lost SSH key, can't SSH into the device


I have FX30 Octave version. As you may have concluded from the title I can not SSH to the device anymore. Previously I enabled authentication using key pair and it worked successfully. Then I set dropbear (/etc/default/dropbear) to disable password logins. For some reasons I lost the SSH key and cannot SSH to the device anymore. Resetting device via ‘Reset button’ doesn’t help. The reset button was never disabled on this device.
Is there an chance to bring that device to its pristine state?

Many thanks,

Does this work?

Thanks @jyijyi.
I connected to AT Modem, mapped Linux Console to UART2 using AT command at!mapuart=16,2.
Then I could only reach that UART by plugging one of RS232 DB9 cards (by Renfell) into IoT expansion connector inside the FX30 and hence get access to the console…