Check your codes, if you are using SoftwareSerial Library and the assigned pins to RX (D2),TX (D3). On the SIM800L shield there's a slide switch for serial select use SUART pin (2,3).
Check your codes, if you are using SoftwareSerial Library and the assigned pins to RX (D2),TX (D3). On the SIM800L shield there's a slide switch for serial select use SUART pin (2,3).
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