The most possible reason is the PDF printer is not ADOBE compatible.
Please check this article
http://www.halfpricesoft...line-checks-printing.asp If it does help, please give us more details:
1. Are you using the latest version ezCheckPrinting and virtual printer now?
2. Your QuickBooks version? online or desktop? 2015 or 2014 or 2013 ...
3. Your system: Windows 10, 8.1, 8, 7, Vista or XP?
4. Any changes on your system recently? ie: QB update, Windows update, virus...
Thank you.