It sounds like your calculator is frozen with both the shift-arrows displayed.
I would first of all suggest that you replace both batteries with new ones (a reliable brand from a reliable source). Note the +ve side (side with text) must be visible for both cells when inserted.
(the problem is that the battery low annunciator is not always reliable and low power can cause strange behaviour).
If, with the new cells, it is still frozen then gently insert a bent-open paper-clip into the reset hole (found in the battery compartment).
You can also try a reset from the keyboard by pressing and holding together ON, N and FV buttons, and release in reverse order. You should see a message COPr HP 2010 followed by ALL CLEAr. Press ON the clear the display to 0.00.
If these resets do not help, remove the batteries for a couple of days and then try again. (This discharges any internal capacitances and can remove a latch-up condition).
If the above doesn't help then you need to call HP support for your area (you should find this towards the end of the PDF manual).