Well since it's a long time ago since you flashed a ROM you may need to update TWRP too. I can highly recommend this one:
TWRP HH for Nexus 5 About: TWRP is an open source, community project. TWRP development is done by roughly 4 people at this point. We also have a large support community with many people who are willing to answer questions and help people with...
forum.xda-developers.com
I'm not completely sure if you can flash the new unofficial builds on top of an old official version of this ROM so don't forget to take a backup before flashing the ROM.
Flashing the ROM is very simple:
Updating without wiping data instructions, aka dirty flashing:
1. Copy the ROM zip, Gapps zip and the Magisk zip to your device. (both Gapps and Magisk are optional)
2. Boot into Recovery.
3. Flash the ROM zip.
4. Optional: Flash the Gapps zip.
5. Optional: Flash the Magisk zip.
6. Wipe Dalvik / Art Cache & /Cache.
7. Reboot to System.
Clean flashing instructions for in case dirty flashing does not work:
1. Copy the ROM zip, Gapps zip and the Magisk zip to your device. (both Gapps and Magisk are optional)
2. Boot into Recovery.
3. Wipe Dalvik / Art Cache, /System, /Data & /Cache.
4. Flash the ROM zip.
5. Optional: Flash the Gapps zip.
6. Optional: Flash the Magisk zip.
7. Reboot to System.
That's it, good luck!