We are not able to push incoming SMS to your SF org due to wrong credential in SMS Magic settings. It seems that your Security token has changed recently.
Please re-enter your all credentials (salesforce User Name, Salesforce Password, Salesforce Security Token) in :
SMS Settings Tab -->Incoming SMS Settings --->SMS Pull Auth Access (Please check the screen-shot for quick reference).
Once you save the correct credentials, please send test message on "447507334446" from your mobile and see if the incoming is getting logged under "Incoming SMS" tab.