tested with a nano, not working

[bbd666]

minimal example application returns:

--=Debug Output Mode=--

Wait for new minute...

unexpected DCF77 connection timeout

Invalid date received.
0:0

[erik-404err]

i always saw this kind of output when there is literary nothing connected to the DCF Pin. Maybe your board cannot get a signal? Persanly, a LED (with resistor) between SIG and ground helped a lot. You can see interference and also notice when there is literary no signal.
hope this helps you