Which version of the One? M7 or M8?
What version of the software did you have on the phone before you started?
What version of TWRP are you using?
Are you S-On or S-Off?
If you are S-On - Did you flash the boot.img via fastboot after you flashed the rom?
Did you make a backup before you flashed the new rom?
Does TWRP still see your internal storage, or does it report it empty or 0 MB?
Do you have a PC handy with adb and fastboot set up?
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HTC Droid Eris / Motorola Droid / Samsung Galaxy S Fascinate / Motorola Droid X / LG G2x / HTC Evo 3D (x2) / Samsung Epic 4G Touch (Sprint S2) / HTC Amaze / Samsung Galaxy S3 (International) / Samsung Galaxy Note 2 / Nexus 4 / HTC One / Samsung Galaxy S4 / Sony Xperia ZL / Nexus 5 / ? (One+1 maybe...)