Issue with white/blank "menu" with PDF Portfolio (Adobe DC and Reader X)

Hi,

Similar to another person's previous question, my organization is transitioning to Windows 10 and a standard desktop/laptop image has Reader X but not Flash player. PDF Portfolios I am creating in Adobe DC can't be navigated under Reader X. The user gets the prompt to download/install Flash Player. When they dismiss it, they can view the first PDF in the portfolio but can't access the others. The "left nav" is blank/white, which suggests Flash is the culprit but my understanding is that Flash is not leveraged or required for PDF Portfolios created under DC. Is there a setting or detail am I missing here?