Dropbox App Windows 10: Authorizing App fails repeatedly but log in to Dropbox using browser works

[FritzTheBox]

Yesterday, I set up a new Windows computer and migrated Dropbox, which I already used on other machines, one of it on the same network. I logged out on the old machine (because Dropbox Basic allows only three apps running at the same time) and, when installing and authorizing the app on the new computer, which is done from the "Welcome to Dropbox" and Button "Sign In", after entering credentials and completing the two factor authentication code, the Browser became laggy, stopped working and showed a network timeout. I repeated it 10 times with the same result. I noticed that when I access https://www.dropbox.com/home in browser after doing all of the above, I am logged into the web interface though. So far so good. Then I switched back to the old PC which was running before but where I was logged out for hours now, trying a reapply log in there, with the same result. The App does not complete, saying "Waiting for sign in" in tray (I only have the German hover text which says "Warten auf Verknüpfung mit Dropbox Konto". 

There is no firewall issue. Browsers tried: Firefox / Chrome. No script blockers, no popup or cookie blockers.

[Jay]

Hi @FritzTheBox, thanks for bringing this to our attention.

Could you try an advanced reinstall of the app using the steps in this link?

Keep me updated with any progress!

[FritzTheBox]

Yes I did. Deinstalling Dropbox, manually removing folders and registry keys, same result. I even installed Dropbox on another completly fresh windows machine. Also tried a 4G/LTE mobile hotspot to bypass any firewall or network influence of my cable internet connection. Checked windows defender firewall for blocked packages, no result.

[Jay]

Is this a company-managed device or a personal machine? Do you have any proxy, VPN, security software, or even ISP/router settings that could be restricting traffic to the following Dropbox domains?

[FritzTheBox]

I tested it on personal machine as well as Company Network and 4G/LTE mobile hotspot, same result. Meanwhile I noticed that https://dropbox.com is NOT reachable (ERR_CONNECTION_TIMED_OUT), while https://www.dropbox.com is REACHABLE. The authorization call uses a redirect_uri to https://dropbox.com - weird? I am accessing from Berlin, Germany.

Here is what TRACERT returns on dropbox.com:

> tracert 162.125.248.18

Routenverfolgung zu 162.125.248.18 über maximal 30 Hops

1 <1 ms <1 ms <1 ms OPNsense.localdomain [xx.xx.xx.xxx]
2 <1 ms <1 ms <1 ms telfr9.lille.imaginet.fr [195.68.11.26]
3 1 ms 1 ms 1 ms h-62.96.36.150.host.de.colt.net [62.96.36.150]
4 <1 ms 2 ms <1 ms 212.74.70.25
5 1 ms 1 ms <1 ms dropbox-v4.bcix.de [193.178.185.125]
6 * * dropbox-v4.bcix.de [193.178.185.125] meldet: Zielnetz nicht erreichbar.

Ablaufverfolgung beendet.

EDIT: New insights: The above only occurs on IPV4 networks. I testet it on my home router, where IPV6 was enabled. A ping to dropbox.com gave an IPV6 address and I could sign in the App with ease. Turning off ipv6 on this machine under Network Adapter Settings remained a working Dropbox App but when signing off and in again it stuck. It seems that at least from my router there is no working IPV4 route to dropbox.com, failing at "dropbox-v4.bcix.de". So a workaround will be to have IPV6 enabled until this is fixed by the German ISP "bcix.de".

[FritzTheBox]

dropbox.com is still not reachable for me since 21.03.2024 and likely only for IPv4 connections.

Steps to reproduce

Go to https://www.uptrends.de/tools/uptime

Fill in "dropbox.com" from "Europe"

Press "Test Starten"

Result

TCP Connection Failed

for

Hamburg

Berlin

Any help?

[Megan]

Hey @FritzTheBox, out of curiosity: have you tried clearing your current browser's cache, and then re-starting your device at all? 

I also found some relevant steps in this thread, that you might want to try out. 

Let me know of the results!

[FritzTheBox]

Hey @Megan, thank you for your ideas. My browser‘s cache is cleared each time I close Firefox. The hosts file is inconspicuous. I testet it on five independent machines with the same result. Instead, the analysis of uptrends.de shows what is really going wrong if testing on a IPv4 network. This corresponds with my results of the tracert call. I think, Dropbox‘s network specialists have to keep busy with it.

[Megan · Accepted solution]

In this case, and since clearing the browser's cache didn't work, can I send you an email, in order for us to have a closer look into this @FritzTheBox?

[FritzTheBox]

Today, accessing dropbox.com from Berlin was successful.

Even a call of "tracert" shows a success now:

Routenverfolgung zu dropbox.com [162.125.248.18]
über maximal 30 Hops:

1 <1 ms <1 ms <1 ms OPNsense.localdomain [xx.xx.xx.xxx]
2 <1 ms <1 ms <1 ms gigabitethernet4-lo0-ber-ic-000332.ia.colt.net [195.68.11.26]
3 1 ms 1 ms 1 ms h-62.96.36.150.host.de.colt.net [62.96.36.150]
4 6 ms 3 ms <1 ms 212.74.70.25
5 27 ms 1 ms <1 ms dropbox-v4.bcix.de [193.178.185.125]
6 1 ms 1 ms 1 ms 185.45.11.25
7 <1 ms <1 ms <1 ms 162.125.248.18

Ablaufverfolgung beendet.

IMHO it was a networking problem situated in the Berlin/Hamburg region I think. Now solved after 5 days.