Possible reasons below.
・Running out the rest of data you purchased
Please purchase additional data usage here.
3.Get “data pack” for high-speed internet!
・Different SIM is selected in the device settings
Please select correct SIM you purchased for this time.
・Outside of the coverage area and/or poor signal reception
Please check if you can use the service with normal speed at another location.
・Setup has not been completed after making the contract
Please check how to configure settings here.