(Re)Install TWRP

Example using OnePlus One (codename: bacon).

1. Download platform tools: https://dl.google.com/android/repository/platform-tools_r29.0.5-windows.zip.
• unzip
2. Download TWRP: https://dl.twrp.me/bacon/
3. Reboot device to fastboot (Vol-Up + Power)
4. Open CMD as Admin, go to platform-tools
5. fastboot flash recovery twrp-3.3.1-0-bacon.img
6. fastboot boot twrp-3.3.1-0-bacon.img

Device will open TWRP.