Make sure you are not blocking content.

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

One issue that seems more common lately is Firefox's Tracking Protection feature. When it is blocking content in a page, a shield icon will appear at the left end of the address bar next to the padlock icon. This article has more info on managing this feature: Tracking Protection {web link}

FredMcD said

Make sure you are not blocking content. Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

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One issue that seems more common lately is Firefox's Tracking Protection feature. When it is blocking content in a page, a shield icon will appear at the left end of the address bar next to the padlock icon. This article has more info on managing this feature: Tracking Protection {web link}

Wow, I didn't try safe mode because I was sure it wasn't one of my add-ons (I was having this issue before I installed them). But law on behold, after I did what you said the issue was fixed. Even after I restarted Firefox in regular mode the issue was fixed.

Was it my Firefox's content blocking that was causing the issue? So does safe mode also change Firefox's content blocking settings? I'm still not sure what caused this, but I'm sure glad it's fixed. Thanks for your help!

Good to hear. No way to know the cause unless it happens again.

Hi LEO96:

My guess the problem was caused by one of your add-ons which were according to the troubleshooting info you submitted :

    AdBlock 3.20.0 (jid1-NIfFY2CA8fy1tg@jetpack)
    Cookie AutoDelete 2.2.0 (CookieAutoDelete@kennydo.com)
    Iridium for YouTube 0.2.2 (iridium@particlecore.github.io)
    New Tab Override 14.1.0 (newtaboverride@agenedia.com)
    Panel View for Google™ Translate 0.3.7 (jid0-fbHwsGfb6kJyq2hj65KnbGte3yT@jetpack)
    Popup Blocker Ultimate 9.6 ({60B7679C-BED9-11E5-998D-8526BB8E7F8B})
    uBlock Origin 1.17.2 (uBlock0@raymondhill.net)
    Video DownloadHelper 7.3.5 ({b9db16a4-6edc-47ec-a1f4-b86292ed211d})

But it could also be content blocking, malware, your isp, your firewall, your wifi router, etc etc

Cheers!

...Roland

Roland Tanglao said

Hi LEO96: My guess the problem was caused by one of your add-ons which were according to the troubleshooting info you submitted :

    AdBlock 3.20.0 (jid1-NIfFY2CA8fy1tg@jetpack)
    Cookie AutoDelete 2.2.0 (CookieAutoDelete@kennydo.com)
    Iridium for YouTube 0.2.2 (iridium@particlecore.github.io)
    New Tab Override 14.1.0 (newtaboverride@agenedia.com)
    Panel View for Google™ Translate 0.3.7 (jid0-fbHwsGfb6kJyq2hj65KnbGte3yT@jetpack)
    Popup Blocker Ultimate 9.6 ({60B7679C-BED9-11E5-998D-8526BB8E7F8B})
    uBlock Origin 1.17.2 (uBlock0@raymondhill.net)
    Video DownloadHelper 7.3.5 ({b9db16a4-6edc-47ec-a1f4-b86292ed211d})

But it could also be content blocking, malware, your isp, your firewall, your wifi router, etc etc

Cheers!

...Roland

Considering the amount of "content blocking" add-ons I have, it's remarkable that anything gets through at all :D

But I doubt whether it was any of them, as I was having this issue before I installed them. And many of those add-ons I have been using for a long time on other computers too, without any trouble. So I guess that also rules out my isp, firewall and router which haven't changed either.

So by process of elimination I'm guessing it probably had something to do with Firefox's integrated content blocker. As this is the first time I'm actually using it (I had an older version of Firefox on my other PC because the hardware was too outdated to upgrade).

If it is Firefox's own content blocker then I imagine a lot of people are having the same problem.

UPDATE 1: I just encountered the issue again. And after some digging around I've finally found the cause of the problem.

It seems FredMcD's suggestion and my own suspicions were correct after all. It was Firefox's own content blockers which were causing the issue.

I disabled all tracker blocking options and "Deceptive Content and Dangerous Software Protection" and now everything works fine. Just for the record, I was trying to install Steam and VLC media player from their own websites, so I'm sure that neither of those were deceptive or dangerous content (in which case they would have been correctly blocked).

So hopefully this will help someone reading this.

UPDATE 2: It seems that what I suggested in UPDATE 1 only worked temporarily.

The problem has now returned :(

Have you tried running Firefox in Safe Mode as I suggested?

FredMcD said

Have you tried running Firefox in Safe Mode as I suggested?

Yes, and like I said; that fixed it, but only temporarily. It came back the next day.

Disabeling all of Firefox's content blockers and security measures also fixes it temporarily. But then it comes back.

Interestingly (and what I forgot to mention in my original post) is that when I cancel the download and then reload the cancelled download, it does complete fully.

So it isn't that I can't download anything, it's just that it doesn't complete initially.

Start your Computer in safe mode with network support. Then start Firefox. Try Secure websites. Is the problem still there?

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode Starting Any Computer In Safe Mode; Free Online Encyclopedia