Check two things:
1) Is your app compiled for x86 or x64? If it's compiled for x86, then you can't access 64 bit Access drivers (or any other 64 bit code).
2) Check the version of the ACE engine you installed: V12 relates to the Office 2007 version, V14 is Office 2010. Your connection string specifically references teh 2007 version.
This may help:
Simple SQL Connection String Creation[
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