Today I wanted to assist a colleague at setting up his Speedport LTE.
The signal strength was “very good”, so I did not expect problems from this direction. My first try with connecting resulted in a “Errorcode 18” message and the LTE symbol in the webinterface stayed red. After some digging in the T-Online forums some threads by other help-seeking people appeared, but nothing really usable.
The key to the mystery: before I try to put any (mobile communications) hardware into operation, I should have a look at the order confirmation to find out when my contract will actually be activated. The “Errorcode 18” is displayed when the contract is not yet activated. Shame on me.