<html><head></head><body><div style="font-family: Verdana;font-size: 12.0px;"><div>I'am have no experiences with writin C++ apps but on the python side you have to set the prefix paths and init qgis at app start. Otherwise you'll get strange errors, like yours.</div>
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<div>QgsApplication.prefixPath() --> get your path from a working QGIS python console</div>
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<div>QgsApplication.setPrefixPath(<path>, True)<br/>
QgsApplication.initQgis()</div>
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<div>Hope this helps.</div>
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