There could be several reasons why your chart doesn't appear once you have inserted your data.
First, the data might be inserted incorrectly. When you choose a chart type, double click on it. Before you paste or import your data (using the import buttons above the data table), take a look at how the example data is presented. Any data you copy and paste or import needs to have a similar layout to display properly.
Also, make sure you are using the correct separator type (either comma or dot) that best suits your data. You'll find number format and separator options under the Data format tab at the bottom of the right sidebar.