The 502 Bad Gateway error you get when trying to generate a report using the jsreport-xlsx plugin can have various causes. One of the most common causes is a memory problem or insufficient resources on the server. You can try increasing the amount of allocated memory for Node.js or increase the amount of resources on the server. It's also worth checking that the version of the jsreport-xlsx plugin is compatible with the version of jsreport you're using. You may need to update one of these components. Another reason that can cause a 502 Bad Gateway error when using jsreport-xlsx is that the amount of data you are trying to process is too large. In that case, it may help you to adjust plugin parameters such as xlsx.maxRows and xlsx.bufferSize to suit your needs. I hope that my information will help you solve the problem of 502 Bad Gateway error when using jsreport-xlsx.