Same bug here

System
Wacom driver version 6.3.36-2 (latest)
MacOS 10.14.6

Blender Version
Version 2.80 (2.80 2019-07-29)

Short description of error
Can not 3D rotate with buttons on Wacom pen acting as middle click.
Software other than blender does recognise the middle click, but blender 2.8 seems ignorant to whatever I setup in the Wacom settings.

[update]
If the Blender Preferences window is active it does work, but when the blender window is active it ignores my settings.

This working fine here:

System Information
Operating system: Linux-5.3.12-200.fc30.x86_64-x86_64-with-fedora-30-Thirty 64 Bits
Graphics card: GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 440.31
version: 2.82 (sub 6), branch: master, commit date: 2019-12-27 20:38, hash: rBc2a37867f21b
(also tested 2.80 release)

I am on macOS 10.15.3 with fresh install of Wacom driver 6.3.38-3 with "Application > All" (also tested a Blender app-specific setting) set to top button as Middle Click.

In blender 2.82 (Left-click as select), it triggers a left-click instead of middle-mouse so it is impossible to use a stylus without Emulate 3 Button Mouse.

I tested making the top stylus button a right click (in Wacom prefs) and it works in Blender so I would assume it is not an issue on Wacom's end.

Windows 10
Intel i7-8700K
GeForce GTX 1080 Ti
Huion Kamvas Pro 22 (2019)
Pen buttons: one on Mouse Middle button, one on Mouse Right button

I have related issues since updating to Blender 2.83.x
(During the same time there was a major windows update so it might be interconnected)

a. In Wintab mode pen pressure isn't working. Mouse-Right pen button Middle and Mouse-Middle pen button do work.
b. In Windows Ink mode, pen pressure is working fine but the Mouse-Right pen-button and the Middle Mouse pen button aren't working in any workspace.
c. To test if this is just a pen button issue I have set up a screen button to Mouse-Right button and one to Mouse-Middle button. Both work in WinTab mode but do nothing in Windows Ink mode.

Changing settings in the Windows Ink Preferences didn't make any difference in these issues.

In T68057#989335, @Simone Lipschitz (illussimo) wrote:

Windows 10
Intel i7-8700K
GeForce GTX 1080 Ti
Huion Kamvas Pro 22 (2019)
Pen buttons: one on Mouse Middle button, one on Mouse Right button

I have related issues since updating to Blender 2.83.x
(During the same time there was a major windows update so it might be interconnected)

a. In Wintab mode pen pressure isn't working. Mouse-Right pen button Middle and Mouse-Middle pen button do work.
b. In Windows Ink mode, pen pressure is working fine but the Mouse-Right pen-button and the Middle Mouse pen button aren't working in any workspace.
c. To test if this is just a pen button issue I have set up a screen button to Mouse-Right button and one to Mouse-Middle button. Both work in WinTab mode but do nothing in Windows Ink mode.

Changing settings in the Windows Ink Preferences didn't make any difference in these issues.

Hey!
My specs:
Win10
Core i7-7500U
GeForce 940MX
Huion Kamvas Pro16 (2019) & Wacom Intuos Pro PHT-660

I have the same issue as described above. I use two tablets and aware of incompatibility of Huion and Wacom being installed on the same system. But they both support Windows Ink and have pen pressure feature as well. But here comes the problem of not working Middle Click Button (besides Kamvas has both Right and Middle Clicks inaccessible when Wacom has issue with the Middle Click only). Yes, all features work in Wintab environment (for Wacom, of course), but it's a pain to reinstall tablets' drivers all the time to make either Wacom's or Huion's technology work, so I use Windows Ink where it's possible instead. But this problem is specific for Blender

My issues have been solved. As I mentioned it had something to do with a Windows update. Drivers are complicated. Pen pressure is back for WinTab and now my pen middle mouse button and right mouse button work as should. I would advise to not enable Windows Ink in the tablet driver nor Blender if you work with a Wacom or Huion tablet or pen display. (Only use Windows ink if you use a Microsoft surface pen or another blue tooth pen.) I also don't let Blender chose automatically. I keep it on WinTab.
I don't know if it was related to Blender updates, probably more with Windows updates. I'm not sure if this still has to be looked at by the Blender developers, maybe it does, to prevent things breaking in the future.

In T68057#995163, @Simone Lipschitz (illussimo) wrote:

My issues have been solved. As I mentioned it had something to do with a Windows update. Drivers are complicated. Pen pressure is back for WinTab and now my pen middle mouse button and right mouse button work as should. I would advise you to not enable Windows Ink in the tablet driver nor Blender if you work with a Wacom or Huion tablet or pen display. (Only use Windows ink if you use a Microsoft surface pen or another blue tooth pen.) I also don't let Blender chose automatically. I keep it on WinTab.
I don't know if it was related to Blender updates, probably more with Windows updates. I'm not sure if this still has to be looked at by the Blender developers, maybe it does, to prevent things from breaking in the future.

Hi!
specs :
win10
ryzen 3 3550h
gtx 1650
veikk s640

I have the same issue as described above. I've been stressing out searching for the solutions, but I found nothing. did you roll back your windows version? if you did, may I know what version you roll back into? thanks!

@Bagus Mars (Mars)

I have the same issue as described above. I've been stressing out searching for the solutions, but I found nothing. did you roll back your windows version? if you did, may I know what version you roll back into?

Sorry to be late with my answer. I did not roll back my Windows update. It was resolved after another Windows update where WinTab was working well again. Windows Ink is just made for one button pens so disable Wndows Ink and only use WinTab. Also like I wrote before, don't let Blender choose automaticly but put it standart on WinTab in the preferences.
I hope this resolves your pen issues.