The rank displayed is not my current rank

The application display the rank detected in the more recent demo (based on date) which has been analyzed. If the rank displayed isn't your current rank it means that you didn't download and / or analyze your last demo.

I don't see any data on graphs

Data are calculated weekly, if you don't see a graph it means that you have only demos of 1 week. The other possibility is that you didn't analyze demos.

Damages graph show nothing until May 2015

It's because damages stats are available only in demos created after the 30/06/2015 CSGO update.

I can't see ranks on the scoreboard

Ranks are available only with demos from Valve Matchmaking.

Some demos aren't included in stats

This is probably because you changed the dates filter and this demos aren't in the interval. You can change it from settings.