Tested on :

FF Nightly version : 67.0a1 (2019-02-13)
OS : Windows 10 Pro

Followed QA steps as mentioned in bug 1525413.

• Set the pref browser.newtabpage.activity-stream.discoverystream.config to {"enabled":true,"show_spocs":true,"layout_endpoint":"https://getpocket.com/v3/newtab/layout?version=1&consumer_key=40249-e88c401e1b1f2242d9e441c4&layout_variant=dev-test-all"}
• Load up a new tab.

Actual Result :
Nothing happens. It has the default New Tab experience (variant =basic). New Layout is not loaded.

Expected Result :
New Layout is expected.

Note: : Tried using the other end-point with extra space after dev-test-all" , but still layout isn't loaded.

Recording :
https://www.dropbox.com/s/ueyzl395xtvczjj/QA%20Results%20%3A%20bug%201525413%20%28Fail%20on%20Windows%2010%29.mp4?dl=0

The video shows it's not even showing basic before trying to switch to dev-test-all. It's showing the original new tab functionality without discovery stream.

What's the value of browser.newtabpage.activity-stream.discoverystream.optOut.0 ? Or if you can share a screenshot of what shows up when you search for "newtabpage.activity-stream"

This is what I have.

browser.newtabpage.activity-stream.discoverystream.optOut.0 = false

"newtabpage.activity-stream" ^^

Those screenshots look to be from the mac firefox and not the windows vm firefox. Could you check the preferences on your windows profile?

This worked for me in my personal windows machine which is using windows 10 home.

Sorry about that.

On Windows I have

pref browser.newtabpage.activity-stream.discoverystream.optOut.0 = true

After setting pref browser.newtabpage.activity-stream.discoverystream.optOut.0 = false it worked.

Initially using dev-test-all loaded everthing in one shot. Then using end-point with extra space after dev-test-all" , I could see delay in response. Page took ~8 seconds to load.

Again switching between these 2 values, had not much delay.

I have done another test on actual Windows 10 Pro N machine and don't see any delays.

Works as expected, everything loads in one shot.

Tested on: FF Nightly version : 67.0a1 (2019-02-14)

Closing as verified.