However, the error suggests you are not using a Spreadsheet::XLSX object when calling the add_worksheet method. 

Which can mean (EDIT: among other things, see Re: Issues with XLSX.pm, in this node by Anonymous Monk) that he does not check if the call to create the object was successful:

my $excel = Spreadsheet::XLSX->new('test.xlsx', $converter);
die "failed to create" unless defined $excel;
[download]

It's likely that instantiation failed because an XS module was not re-compiled re: In the middle of server upgrade because nobody told it to or simply failed.

PS. I would like to see more error checking in Synopses, just for these cases. People just copy-paste that code without too much pondering.

bw, bliako