The best way to contact us is to post a message in this forum. We and other users can carry on a discussion to try to work out what problem you might be having and how to solve it.
Reporting problems or asking for help in reviews on Google Play is the most difficult for us. Our first problem is contacting you for more info; it isn't easy to find an email address for a reviewer, and might be impossible. The second problem is that other people who might have solved the problem cannot answer at all. The third problem is that we can't be sure that you even want a response and that you might consider us contacting you an invasion of privacy. We are not suggesting that people should not leave reviews, good, bad, or indifferent. Instead, we are suggesting that if you want support from us, a review is not the best way to go about it.
It could be that we will need a calibre debug log to help analyze the problem. You can get a calibre debug log by running calibre in debug mode. Start calibre, then click the small down arrow next to preferences as shown in this screenshot.
Click on "Start calibre in debug mode". Let calibre restart and answer OK to the dialog that confirms that calibre is in debug mode. Attempt to connect CC to calibre. Get to where you are having the problem, then close calibre. You will see a debug log in a new window, probably in a text editor. An example is
Copy all the text in that window and send it to the email address provided in the thread. Alternatively, attach it to the thread where we are having the discussion. Do note that there might be information about your library in the log that you do not want public, in which case don't post it. Please do not paste the log into a post. It will lose formatting and be too long to easily analyze.
When you send a calibre debug log you should also send one from CC. To send a CC debug log, go to CC's settings, scroll all the way to the end, and choose "Send a debug log to MultiPie". When given a choice of which app to use to send the log, pick your email client. You should see a message open addressed to us, with the debug log as an attachment. We might ask you to remove one or the other of the standard "To:" addresses you see in that dialog.