I may have found a possible explanation.

It worked for a couple hours after the initial setup.

Tonight, I did a factory reset and reproduced the original configuration and got the VPN client to work again.

One configuration that works is having a single VPN Client configured and NOT configuring QOS to the Android streaming device. (Note: thinking back, it really seems to be the act of configuring QOS to the device while the device is used with the VPN Client that caused the problem. After that action, there was no going back. I only regained the VPN Client functionality after resetting the router to factory defaults.)

I'm not willing to break the configuration again on purpose so I won't be adding another VPN Client for now and I will also not setup QOS on the Android streaming device.

Every time I need to reboot the router and/or wipe the configurations, I cut the internet to my whole house and family.

Note that ALL the behaviors are repeatable on connected devices of any type. In fact, I used my iPhone and my Windows PC to reproduce and troubleshoot the problems I had with the Android streaming device.

Hi tp-link!

I put efforts into my post and it would be nice to have this problem acknowledged first, then have a fix planned and delivered.

Even though I can now use all the devices in my house, I'm still interested in using all the features provided by the router. Right now, it seems I cannot use QoS with the intended device.

Thanks in advance! :)

Still no input from TP-Link on this issue. Still relevant. 

Please acknowledge.

  @Kevin_Z 

Hey, thanks for answering. I'll try to answer the best I can, it's been a while.

• Just a quick confirmation, how do you use the QoS feature for these devices?

I'm not sure what "how do you use the QoS feature" means.

If you're asking "how would I go to enable the feature", I logged into Tether, activated the feature and added a device.

If you're asking how I actually USE QoS, I have not actively gone through more setup than this. I activate the feature, add the device and trust it will work.

• Will they lose the connectivity as soon as you toggle to enable the QoS option?

Not that I can remember.

• Or does it issue happen after you add the device to the High Priority list?

This is how I remember it. It would stop working after being added to the list while connected to the OpenVPN client functionality offered by the router. Since I always planned to have the device connected to the VPN, I don't remember actually trying to enable QoS first, then connecting to the VPN. As this bricked the whole device's connectivity, I didn't do a ton of testing before stopping trying to use QoS.