Have you updated the app recently? Please try uninstalling and reinstalling the app from the Playstore (Andorid) or the Appstore (iOS). Alternatively, you can go to your Phone Settings > Apps > TagMango and then Clear Storage/ Clear Cache. 
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If your network is working fine and the issue still persists, kindly reach out to support@tagmango.com with a screen-recording of the issue, your name, your registered mobile number, email, the device model number and whether your device is Android or iOS. Once you share the complete information, the team shall resolve the issue within 72 hours.