Unable able to open websites in Firefox only

VPN
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Some (common urls in my workflow) urls don’t open in firefox.

Ex: https://kconrad.math.uconn.edu/blurbs/linmultialg/diffeqdim.pdf

http://www.mathcs.emory.edu/~cheung/Courses/171/Syllabus/9-BinTree/bin-tree.html

They open perfectly fine in other browsers. I am having to switch browsers just to open these urls which is very frustrating.

Please help. I have already tried setting below options in about:config

- setting security.enterprise_roots.enabled = true

- network.dns.disableIPV6 = true

- Tried with all the network proxy options

- disabled all extensions

EDIT: Thanks for all your comments - It might be a dns issue in firefox. I have forced the dns to cloudflare in network settings. Hope it fixes the issue. Atleast the above two sites are opening. Will update if i see this error again.

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Try to flush your dns cache.

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Try changing your DNS?

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I’m not having any trouble with those on Firefox myself, so it’s not a a problem with the browser itself and those URLs. The error message could indicate a DNS problem. Not with the wider DNS system, but potentially with Firefox’s implementation. Have you tried disabling DNS over HTTPS? It’s in Settings → General → Network Settings → “Enable DNS over HTTPS”

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Both open just fine for me.

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I see that on my company computer when I let the VPN expire and firefox will not reset the connection when I reconnect to the VPN. I have to close all Firefox windows and reopen

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Try with Refresh Firefox - reset add-ons and settings | Firefox Help

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why did i open this :[[ bad memories

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First site resulted in nothing loading today. I thought they fixed that bug?

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I had an issue like this after messing with about:config settings but I can’t remember exactly what change did it.

I’d look at your modified about:config settings and play around with resetting settings you suspect could be responsible and testing to see if any of the changes resolves anything.

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That’s the thing - It’s not very consistent with these urls. Sometimes they open and sometimes they just refuse. But on other browsers they consistently open.

Yes, I have turned off ‘DNS over HTTPS’ .

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Try waiting 60 seconds for the DNS cache to expire or go to about:networking#dns and click the “Clear DNS Cache” button.

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Try resetting FF’s certificates. Chromium browsers use system certificates, FF uses its own. I had the same issue as you and resetting them fixed it.

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Is there anything useful in about:networking#dns and do you get a proper response for those domains in about:networking#dnslookuptool ? (Don’t worry about NS_ERROR_UNKNOWN_HOST under HTTP RRs)

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Go to Network Settings and try changing “Use system proxy settings” to “No proxy”.

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I have reset the certs now. Let me try more browsing and report back. Thnx.

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I see other dns entries but not for these. dnslookuptool is returning response. Let me see tomorrow. I ll open up some more sites and look again.

Btw, if i open site in a chromium browser and come back try it again on firefox, it works. Does this give any ideas to why ?

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