I am trying to join a .csv file to a layer in QGIS 2.18.6. For that I created a .csvt file. However, I am not able to join the two files. I tried it with the key both as integer and string but in both cases it didn't work. When the key is an integer I have the additional problem, that the leading zero disappears in the key column which makes it obviously impossible to link it to the shapefile.
The .csvt file looks as follows:
The .csv file contains in the first column the key and in the rest data. The .shp file only contains a key column in the attribute table.