Possible Reason #1) Incorrect proof text: The verification text needs to be exact, more specifically "Verifying myself: My blockchain ID is +" needs to be in the text. This requirement is because of security reasons and we can't allow arbitrary methods of phrasing the proof text.
Possible Reason #2) Incorrect URL to proof: You can view your profile data by clicking on "Profile Data" on the left-bottom corner of your profile or by appending ".json" to your profile URL. An example of profile data is . Your profile data will list URLs to different proofs. Make sure that if you visit the proof URL (of Github/Facebook/Twitter) you can see the proof text on that URL. This URL needs to be publicly readable (private accounts don't work).