Bump with more info:
After enabling debug mode in wp-config, I get the following error:
Warning: stream_socket_client() [function.stream-socket-client]: unable to connect to tcp://api.www.remarpro.com:80 (A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. ) in E:\kunden\homepages\33\d468997241\www\wp-includes\class-http.php on line 1021
Does this mean the problem is with my host server? If so, any idea on what the fix is?