[OnePlus 7T Guides, News, & Discussion] super michael:
So I did this process yesterday and since this thread was quite valuable to me I feel like sharing some insights.

First of all it is really important to fix "the drivers". If you connect your phone in adb, fastboot or EDL mode you have to figure this out first. Wrong drivers usually can be spotted in Device Manger with a Yellow exclemation mark. Yes - ADB/fastboot and EDL are different drivers.

If you have problems connecting in ADB/fastboot mode download drivers here https://developer.android.com/studio/run/win-usb and install them like this https://developer.android.com/studio/run/oem-usb#InstallingDriver

If you have problems with EDL follow this link: https://xdaforums.com/t/op7t-t-mobi...l-to-restore-your-device-to-oxygenos.4004005/ read "My device isn't detected when I click on "Enum" button"

I usually do not just "install drivers from exe". I go to the device manager, look for uninstalled devices and right-click update drivers so this specific device gets this specific driver. This may be an overkill in 2020/Windows 10 but why change a running system..

You can test those drivers quite easy.

1. First download & unzip the android plattform tools (https://developer.android.com/studio/releases/platform-tools).

2. Enable USB Debugging in Dev-Options on Android

3. Point CLI to your folder where you unzipped said toolset

4. Type adb devices in CLI - if it shows a device your ADB drivers work.

5. Then reboot your device to "fastboot" you can do this with button mashing or since ADB works just type adb reboot bootloader

6. Wait for reboot, then type fastboot devices if it shows a device your fastboot drivers work.

7. Boot back to Android again (click power when it sais "start")

8. Go back to step 3 and type adb reboot edl (again you could boot into EDL with som button mashing but why do it the hard way)

9. To test EDL you have to use the MSM Toolset (patched or not doesn't matter) - if it says connected this means your EDL drivers work too

It is crucial to test this bevore thinking about flashing for obvious reasons. And you learned to boot into all the modes via CLI which is nice.

With this out of the way I would like to add some thoughts to the inital post:

1. When flashing the device (Step 7 in initial post) my device booted into T-Mobile start screen for some reason instead of booting into fastboot and continuing pushing images. This was not the case if I booted into Recovery Mode (fastboot -> choose recovery mode with volume keys -> enter PIN -> choose English -> something something fastboot) and Chose "Fastboot" manually. After this the flashing worked flawlessly

2. I "patched" the tooling (fastboot.exe, adb.exe) from the link in inital post with the latest files from google sdk, this did not work. Use the tools inside "10.0.13-GLOBAL-OnePlus7TOxygen_14.O.19_OTA_019_all_2009281709_1026-FASTBOOT"

3. For easy of use I created my own flash_all.bat with the local reference to fastboot.exe (see attached) as explained in intial post. This goes inside "10.0.13-GLOBAL-OnePlus7TOxygen_14.O.19_OTA_019_all_2009281709_1026-FASTBOOT"

4. Since I was impatient I used the method with the patched MSM Tool to unlock the bootloader - I can confirm this works. After relocking the bootloader picky apps like Netflix work too.

5. I did skip step 3.5 "fastboot boot twrp.img" since I didn't understand what it does - it works without this

Hope this helps.

Thanks for the guide chxc