....many thanks to Modding.MyMind!
THere's two methods. Try whichever works for you! The second is what worked for me!
(1) You'll need to get a stock nanbackup copy of your droids model to restore your OS if you lost it completely....as I did! LOL! You'll need to use TWRP custom recovery to restore from backup your boot, system, recovery and everything else you can restore, but those three are the main ones. Make sure to do a clean wipe first of EVERYTHING before restoring! If your S-ON or even S-Off (Couldn't hurt!), You'll need to Flash through Fastboot mode the Boot.img. using this command > fastboot flash boot boot.img. If your on Mac its > ./fastboot flash boot boot.img
Note: If you don't have a Boot.img, you can make one easily by converting the name of this file boot.emmc.win, which can be found in your backup folder, to boot.img. And for added measure convert recovery.emmc.win to recovery.img and flash that too though it should have flashed already when you restored from backup! Boot.img is the only file that seems to need this extra step using fastboot if your S-On! Don't ask me why! LOL!
(2) After restoring from TWRP, Restart into bootloader, so you can get into fastboot mode and start flashing the boot.img and perhaps the recovery.img for added measure as already mentioned above! Use "fastboot flash recovery recovery.img" to flash recovery. Note: that you will lose your TWRP custom recovery as a result of this. But you can flash that back later after your done getting your droid working again!
METHOD ONE After flashing both images, get out of fastboot mode and back to HBOOT, and try a Factory Reset! This may or may not work, but don't worry! Cause if it does, it will restore your partitions faster than the next step that I tried and succeeded!
METHOD TWO If the HTC Factory Reset doesn't occur and just takes you right back to stopping at the HTC Logo, then remove battery and restart to get back into fastboot mode again, make sure your droid is connected to you PC or Mac, and type in these commands in the order shown, hit return after each command line.
fastboot erase cache
fastboot oem rebootRUU
fastboot flash zip firmware.zip <----(This file you will need to extract it from this zip file ( OTA_K2_CL_JB_45_S_Sprint_WWE_Boost_2.06.653.5-1.11.653.1_release_3244713ijuyqp8g1s0xuaw.zip ]and place it in your fastboot/adb folder so you can flash it straight to RUU. I obtained this file from this thread under RUUs & OTAs "Search and find all what belongs to HTC One SV". YOu can find the model that pertains to you. Mine was this one for Boost Mobile USA version, not international! The Firmware.zip found in the file reset everything without losing root or unlock feature!)
./fastboot erase cache
./fastboot oem rebootRUU
./fastboot flash zip filenamehere.zip
When the firmware.zip is finished uploading loading, (you should see a green bar finished loading), then type this command "fastboot reboot" ( "./fastboot reboot" if your'e on mac...minus the quotation marks! LOL!) and now wait for it..........SUCCESSSSSSSSSS! LOL!
---------- Post added at 12:14 PM ---------- Previous post was at 12:03 PM ----------
If nothing happens after you enter "fastboot flash zip firmware.zip" ( You should see a whole bunch of scripts running till it says...OKAY! ), then you'll need to either find the right OTA file and/or try finding and flashing a signed copy of the recovery image, eg...recovery_signed.img that belongs to your particular droid model!
But the stock version should work fine! Fingers crossed! LOL!