Hello, I'm Wes, and I'll be assisting you today.
Sometimes the memory can become full over use and require a restart.
Try holding down the power button for a few seconds until the device powers off.
Also, you can download an app to close open tasks you are not using. This will free up more memory.
Here is a link: https://play.google.com/store/apps/details?id=com.rechild.advancedtaskkiller
Let me know if you need additional help so I can assist further.
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