I am new to QGIS and having trouble exporting. I loaded a shapefile (.shp, .shx, .prj, .dbf) and displayed it on QGIS, which worked fine. The latitude and longitude were not correct, so I chose the .prj as the CRS and it updated to correct lat/long. Only now when I export the geometry to a CSV file, the updated coordinates do not come with it and I get the old coordinates, which won't work as I am trying to get the CSV's into a map on Tableau.
Try saving it as a new shape file with the modified CRS first, then export that new shape file to CSV. This answer seems relevant to your question. CRS reprojection
If that doesn't work, I found a tool that should do the trick. Processing Toolbox>QGIS geoalgorithms>Vector general tools>Reproject layer.