Please note this is a user to user forum not Magix Support.
To upload a screenshot - use the icon to the left of the blue smiley icon above when posting a comment, the image should be in a supported format, eg jpg, png bmp, and cropped to show the error dialog box.
From the error text you have posted this looks like a HTTP 504 error message - 'the gateway server did not receive a timely response form another server'.
Was there a particular action you were doing eg using the Online Catalogue/Gallery at the time the message popped up? If so there may have been an issue with the servers at Magix.