[Nexus 9 Q&A, Help & Troubleshooting] logikol:
How I solved this issue

Hi there,

I was running into the same issue today. I'm new to android so I thought I could just simply load the image-volantis-MPZ44Q.zip into a command prompt and that all would be well. Unfortunately, my N9 bricked and ended up in an endless reboot loop. I saw "google" then a few bouncing balls for a second or two and then the entire process would restart again. (note: I was trying to upgrade from 5.1.1 to M)

Here's how I fixed it

NOTE: I am typing this out from memory. Some steps may be missing. If so, I trust that the rest of the community who is more knowledgeable on this and other related topics will be able to assist.

After hours of research and numerous failed attempts, I was able to bring it back to 5.1.1 using the following method:

1. Google WUBFRESH Nexus Root Toolkit and download and Install it. (I can't post any links because I just signed up to post this message).

2. Choose your model type etc and the android build and hit apply. For me, I choose Nexus 9 (HTC Wi-Fi Tablet) and VOLANTIS-FLOUNDER: Android 5.1.1 - Build: LMY47X.

3. The toolkit should load up now. On the right side under Restore/Upgrade/Downgrade choose "soft-bricked/bootloop" and click "Flash Stock + Unroot". Note, you need to be unlocked for this step. I was already unlocked prior to my attempt at upgrading to M.

4. Plug in your N9 via USB to your computer. If it's still boot looping, wait until you see the google text, then hold the power button and the volume down button until you get either the HBOOT menu or you get an icon that shows the little android guy lying down with his door open (aka recovery mode). If you see a white screen with HBOOT, make sure at the top it says "UNLOCKED". If it says LOCKED, these steps may not work for you!

5. Use the volume buttons to select Fastboot and then press the power button to enter in it.

6. Back to your computer.

7. Press OK to get through all warning screen (read them first obviously).

8. The program will ask you for an image. At the top, choose VOLANTIS-FLOUNDER: Android 5.1.1 - Build: LMY47X from the drop down menu. Under Choice, choose Automatic download + extract. Under Settings, choose "Force Flash Mode". Press OK.

9. It will begin downloading the factory image from the google developer servers.

OPTIONAL:If

the program isn't able to communicate with your device, it may be a driver issue. I used the instructions on the following site: (remove spaces when pasting into your webbrowser) theandroidsoul.com/ nexus-9-driver-adb-fastboot-mtp-installation-guide-68375/ . I had to supplement the instructions by first unplugging my device, then loading it into HBOOT, then choosing Recovery, then choosing apply update from ABD, then plugging in my device. The computer recognized it and it showed up in my device manager with a yellow exclamation mark. I right clicked, went to it's properties and then updated the driver. Then I choose Browse My Files, and choose "let me pick from a list", then I pressed have disk, navigated to where I had downloaded and extracted the usb drivers and selected android_winusb.inf. I selected the first one and continued through all the warnings by pressing next/ok. It was finally complete and the yellow exclamation mark was gone.

10. Once complete, the program may ask you again if you have backed up your files as this is a point of no return. Read the notice and press OK when you are ready to continue.

11. At this point, a command prompt will open up and it will transfer the 5.1.1 files. This took approximately 5 minutes on my end. At the end, there were some instructions that the N9 may be rebooting and that it would take 5-10 minutes. This never occurred for me. Instead, the device went back to the fastboot screen. I then selected REBOOT (the second option in yellow).

12. Finally! The device turned on. The colored balls were flying and after 5 minutes or so, the ANDROID logo came up and I was able to setup lollipop.

Hope this helps...