Hmm. Not mounting internal sd... Try this:
Flash stock recovery in fastboot, then hit factory reset in bootloader. This should clean up any corruptions/bad sectors and make the internal sd mountable again. Once that's done, flash your custom recovery, and try installing stock from sideload again. Make sure both the adb on your computer, and the custom recovery is up to date.
Sent from my HTC One V using xda app-developers app
- HTC One M7 Silver
(2014) running ViperOne 6.2.1
- HTC One V Black
(2012) running Ignorance V5