Hello,
I was able to wire a 1D Array of Waveforms to the "1D Data" input of the "Write to Spreadsheet File" VI without receiving a broken wire. I am not sure why you are getting that error, although I have in the past received similar errors when working with clusters, where the datatype of the source and sink appeared to be the same, and the problem ended up being with the cluster order of the elements inside the clusters. Order is not an issue with Waveforms, though. Perhaps you could attach a simple VI or screenshot that demonstrates the problem?
Good luck, and have a nice day,
Darren