This has happened to me on several occasions with a couple of different HP all-in-one scanner/printer's. The HP driver/program itself may be in a phase where it's attempting to complete a scan, which would prevent you from scanning anything else. You can confirm whether or not this is the problem by restarting your computer and attempting another scan. You'll get an error message saying the scanner is currently in use.
You may want to try to completely remove the installation files for the scanner, and reinstall either from the disk or let windows install it for you via "plug and play". Then update the drivers from hp's website. See if that resolves your problem.
my printer says "offline" when I go to control panel and right click the printer there is...
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my printer says "offline" when I go to control panel and right click the printer there is no "online" switch...I reset something last time and I cannot remember what