Hi,
the URL is http://dmexco-koeln-nrw.de/. The site is actually live and there is no chance to switch to another template the next days.
I tried to reproduce the error in the environment i used to build up that site (http://test1.topiclodge.com). But there jetpack works fine. I have found out that the button "Connect to wordpress.com" links to different targets in both environments:
Working environment (with hashed IDs):
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https://jetpack.wordpress.com/jetpack.authorize/1/?response_type=code&client_id=00000000&redirect_uri=http%3A%2F%2Ftest1.topiclodge.com%2Fwp-admin%2Fadmin.php%3Fpage%3Djetpack%26action%3Dauthorize%26_wpnonce%3Dxxxxxxxxx&state=1&scope=administrator%3Axxxxxxxxxxxxxxxxxxxxx&user_email=EMAIL@DOMAIN.DE
Not working environment:
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http://dmexco-koeln-nrw.de/wp-admin/admin.php?page=jetpack&action=register&_wpnonce=xxxxxxxxxx
The template, all used plugins and their versions are identical. The only difference is the hosting provider. Everything else is working fine, so maybe Jetpack uses something special to work? You can find phpinfo for both servers:
Working: http://test1.topiclodge.com/php.php
Not working: http://dmexco-koeln-nrw.de/php.php
Thanks a lot!
Greetings from Germany,
Claudio