Mine is black too. hmmmmmm
and the saved XSEQ file is full of "NULL" values
My original test was three event lines, all of them Wave effects. I got nothing out in preview and the file was full of NULLs
Then I changed line two to simple Butterfly, saved, and it plays ONLY the second line. Blank, Butterfly, then blank. The XSEQ file is likewise Null, then data, then Null to the end.