HTC M9 cannot unlock

I have a relocked & S-ON M9.
The recovery partition got corrupted after loading OTA 2.10.401.1 > 2.10.401.180


This prevents the bootloader beeing unlocked.
I tried offline FTM mode but no change in lock status...
Online unlock or S-OFF won't work either



How can I flash a recovery or get it unlocked?