I do not believe the Acer Iconia B1-A71 is classified or supported as a USB-On-The-Go (OTG) device.
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Recently I asked a similar question. Got no single answer. For any Acer technician this should be an easy question however. Maybe it would also be a good idea that there was info available about what features a specific device is offering and (more important) what not. Than unpleasant surprizes after you bought the device would not be needed.
About OTG: your tablet has to support USB host mode, which the B1 does not. I found this out myself the hard way: after I had purchased the tablet.