When you installed did you choose 'yes to all' when asked to overwrite existing files? You will need to do this when installing the newer extension. Also, after it is installed and you get this error have you tried to clear the cache? A restart of your machine might be in order as well.
If doing these things makes no difference then there may be a corruption of the configuration folder, here are some steps you can take for that if it is the issue.
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