It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

There is a problem with setting work ares for copper mines. Despite no underground mining necessary as there are still resources left, immediately after placing a work area one gets the message "Work area exhausted: mine ore".

This problem seems to be known for at least about half a year: