The Import/export buttons are greyed out/disabled, I am not sure what is going on. My account is linked to github and authorized.
Can you make sure you grant github repo access (right above the import/export button). And If that does not help, can you show me a screenshot of the error so I can see if there is anything else, also, just to let you know, you must be the owner of the project to do this!
Finally got it working, not sure what happen, but its fixed now.
Ok! Glad you got it fixed.