Error 7 when attempting to flash ROM I'm trying to replace the stock ROM on my OnePlus 3 in an attempt to find out if another ROM has fixed a set of really annoying bugs present in stock. My phone is running the latest OTA from OnePlus (ONEPLUS A3000_16_170610).

I've followed the following steps:


Flash TWRP and SuperSU. Reboot several times.
Disable lockscreen security.
Boot to recovery and do a full backup.
Reboot and copy new ROM and Gapps to /sdcard.
Reboot to recovery.
Wipe dalvik, system, data, and cache.
Attempt to install the ROM. At this point, I get the following error:

Checking for MODEM build time-stamp 2017-06-27 21:43:31
assert failed: op3.verify_modem("2017-06-27 21:43:31") == "1"
Updater process ended with ERROR: 7
Error installing zip file '/sdcard/RR-N-v5.8.4-20170806-oneplus3-Official.zip'



This example is using the latest Resurrection Remix ROM, but I've also gotten the exact same error from the latest LineageOS.

What's wrong?
This will likely be closed as off topic, but twrp is telling you exactly what's wrong. Your modem does not match the accepted one that you should use. Usually means you need to update firmware (bootloaders, modem, any vendor partitions etc).