Hi, have you read the post: PSA: make it easier to help you? It is very helpful to those reading your question if you follow the conventions outlined there. In particular, it is very difficult to tell which line is throwing the error from the code you have posted, and a “minimum working example” would make it much clearer.
In addition, have you taken a look at the documentation for XLSX? It features a Tutorial · XLSX.jl that could shed light on what is happening.