I bought an Archer VR400, it worked properly in the first few months, but then I found that the internet is intermittent. The router shows orange at that time, and I found this error message on the basic page once I logged into the router-- Please configure your DNS server manually. 

I tried to power cycle/reboot/reset but no avail, I also changed the DNS server manually to 8.8.8.8/8.8.4.4 as the error message. Nothing changed. 

I really like the Archer VR400, my families access the internet perfectly through it and I do not want to waste more money to buy a new one.  So I decided to reach out to the tech support of the TP-Link to get some help, haha, guess what? We sorted it out. It turns out that the upload bandwidth I paid is too low which is not enough for the heavy traffic network activities. And they offer me a beta firmware to solve it. 

Here are the quotation of the suggestion provided/info asked by the tech support, may it help you guys.

1. Please tell the ISP and the bandwidth paid.

2. Show the tech support of the specific symptoms of the intermittent connection which helps them to locate the root cause, and provide the screenshot of the advanced-status page (especially the DSL status page).

3. Show them the current hardware and firmware version of your device. Do not forget to tell the country version, which is important you know, TP-Link has sold their products all over the world, and the device is different due to the countries, even the same model.

Anyway, it is very amazing. The tech support is very helpful. Now my Archer VR400 works properly as expected.

Good job. TP-Link!!! I'm very appreciated.