I was previously using QGIS 2.2 and using the openlayers plugin to display google streetmaps on an area. Reopening the project several months later I found that this layer no longer displays. In fact it displays as blank and white. If the google streetmaps is the top layer it blanks out all the layers below it. None of the other sources on openlayers plugin displays either. Usually, when selected, the map appears with a grid with little question marks in the middle of each square. I uninstalled 2.2 and installed 2.4, 2.6 and 2.8 in sequence, at each stage removing traces of the previous installation. However I can never get anything on the openlayers plugin to appear on any map. I am running windows 7
Make sure you're using the plugin version that is compatible with your QGIS version. You can intall the latest plugin version via the toolbar:
Plugins > Manage and Install Plugins.
Note that using the latest version of a plugin may no longer work with older versions of QGIS.
There is a good answer here by @Thomas which allows you to save different plugin versions for their specific QGIS version.
Just use quickmapservices plugin. This is QGIS featured plugin.