That doesn't make sense , if it worked for two weeks how did you get it to work? A tablet has two options and two different types , one is a connected tablet to a cell service and needs a cell plan to access the mobile network. The other is a non cell service tablet and doesn't have the capability of connecting to a cell mobile network but can be connected to a WiFi network in your home or other place that has WiFi.
Which do you have?
One thing that we don't do here in these forums is help with unlocking or unblocking of devices because we cannot verify ownership or identity.
You can contact the place that the tablet was purchased from and request help or your cell phone provider if it was connected to a cell service.