Several people can access Makerble using the same device, even while they are offline.
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This means that as long as you have previously logged in to Makerble Android using a specific device while you were online, the app will remember your login credentials on that same device so that you can login using that same device while you are offline.
Steps
Open the Makerble App on your device
Unless you or somebody else is already logged in on that device, you arrive on the Sign In screen
If somebody else is already logged in, follow the steps to log them out
On the Sign In Screen, enter your login credentials
Press Sign In
You arrive on the Contacts App