Hm. I’ve just installed the Flattr plugin from scratch — it’s my first time (so I’ve got a clean database!) and I’m a brand new Flattr user.
I have the same issue as @mabahi above. The URL for authentication is the same, the error is exactly the same, the page seems to be the same.
Plugin version is 0.9.25.5. My hosting provider is Dreamhost, which usually has no problems in contacting external sites, with three (possible) issues:
1) Sometimes, Jetpack also fails to connect under PHP 5.3. The solution is to go back to PHP 5.2, attempt to connect, and try again. Should I do the same for Flattr? What do you think?
2) I’m using W3 Total Cache.
3) My blog (https://gwynethllewelyn.net/) runs behind CloudFlare. Again, this usually doesn’t make any difference, but it might — I would probably need to punch a hole through CloudFlare.
I’ve registered another site as a test, which is also hosted on Dreamhost (but with PHP 5.2 FastCGI instead of PHP 5.3), uses W3 Total Cache, but doesn’t use CloudFlare. I got precisely the same errors.
This latter site has an advantage: I can bring it down (it has next-to-zero visitors). So I did the following experiments:
– Downgrade to PHP 5.2 (not FastCGI). Same errors.
– Deactivate W3 Total Cache. Same errors.
– Deactivate all plugins except Flattr. Same errors.
So my guess is that Dreamhost is to blame. Jetpack is also misbehaving, so that could be a hint. I’ll try again tomorrow early morning (less traffic on the ‘net) and see if the problem remains.
And I’ll try to install Flattr on a different hosting provider, too.