plugin repository unavailable

[Julian von Kanel]

Hello everyone. I am new to QGIS and I am trying to learn by using the AN INTRODUCTION TO INTEGRATING QGIS AND R FOR SPATIAL ANALYSIS book. When I downloaded QGIS it came with 22 plugins, but I am required spreadsheet plugin in order to proceed on the first exercise. However it tells me that the plugin repository is unavailable constantly so I am never able to download more plugins. Has anyone else had this problem and if so, how do I fix it in order to continue?

Thank you!