Hi there!
If you are trying to print or to select scan from your desktop, be sure to install the latest software
"HP OfficeJet Pro 7740 Wide Format All-in-One series Full Feature Software and Drivers" from this website
Another thing to note, whenever you load a paper into the tray, be sure to select the right type of media in the control panel before proceeding.
As for the scanning option, if you are doing a copy function, please check that the right paper media size is selected correctly, then make sure that you scroll down and check that the options are properly selected before you hit the copy button. You can choose the option of fit to page, or actual size copy inside the resize options.
If all else fails, please check that that there are no other obvious dirt or particles on the scanner glass or on the foam white backing of the scanner lid before scanning.
If there are any further questions, please describe in detail what function you are doing? Will that be a scan to PC, scan to thumbdrive, or copy function?
Regards,
Samuel