Sometimes, Facebook doesn't recognize your password - even though it's correct - which leads to this connection issue.
As the problem occurs on their side, we unfortunately, don't have any control to solve it but we have found two solutions that work most of the time to fix this issue.
Could you please try to clear your cache from your Google Chrome browser and start again?
If this is not working could you try to login to Iconosquare in an incognito session?
Feel free to contact us if you are still having issues with it all :)