When I sign in, I get the message: Your browser appears to be blocking dropboxcaptcha.com. Why?

Hey there David Harries, sorry to hear you're having issues with this.

Can you please try a private browsing window without any extensions or plugins running and let us know if you notice any difference?

You can also check to see if any plugins or add-ons may be interfering, by disabling them temporarily. 

Thanks!

I am having the same issue trying to login via multiple browsers (including in private sessions).  I have cleared my cache and cookies, restarted, running no plugins and not having issues on any other site.  This is the message I am getting:

Your browser appears to be blocking dropboxcaptcha.com, which is required for authentication. To resolve this issue, please update any anti-virus or ad-blocking software settings to allow connections to dropboxcaptcha.com.

Hey steve_a, sorry to hear you're having issues with this.

If possible, have you tried another wifi network or doing this via cellular data?

A screenshot of the exact error you're getting would also help, so feel free to add one in your next reply. 

Disable IPv6 on your network card. Dropbox doesn't play nice with IPv6. They wont admit it but this solves 99% of issues like this.