There is also another issue, although this one may not be possible to be solved:
The last version of the plugin (4.2.0) calls the replace_with_placeholders() CF7 function, that is not available in all CF7’s versions, so it would be nice to check/set a CF7-plugin minimum version requirement (I don’t know if the version of a dependent plugin can be checked…).
The CF7 plugin only updates to the last compatible version with your current WordPress installation, so you may be stuck with an older one that may not be compatible with this plugin.
I fixed both issues installing the previous version (4.1.0).
