Why won't my LG G4 take screenshots anymore?

[AC Question]

I've had my G4 for a few months and was previously able to take screenshots with the power/volume down button combination, but the last week or so that only serves to turn my volume down and make me incredibly frustrated. I use the QuickMemo capture sometimes, but in some instances, like screenshotting an instagram story, swiping down from the top of the screen to get to quickmemo isn't an option, and the fact the buttons aren't working for me anymore drives me crazy. If I restart my phone, I'm able to screenshot using the buttons maybe once or twice before they stop working again. Help!! And thank you in advance for your feedback.