Maybe there is a problem with the communication between the data logger and the portal. If device errors are ruled out, a simple restart will fix this issue.
To restart the logger:
Press the reset button and wait until LED 1 goes off after approx. 5 seconds. Now release the reset button and after approx. 20 seconds LED1 and LED 2 start to flash. The device is starts now to initialize.
Please do not restart the data logger by disconnecting the power cord!