Xperia L corrupt Cyanogen recovery

Hello guys, desperately need help with xperia l. The phone keeps booting into cyanogen recovery.
I have unlocked the bootloader for cm12. Now I cannot flash a custom recovery because adb command shows device unauthorized and fastboot says <waiting for device>. And when I try to install update.zip it says failed to install sideload package.zip.
any help will be appreciated