I installed the most recent version of this add-on but wasn't being prompted to download a CSV file after clicking 'Export to CSV'. I know little about PHP but I showed my expert brother and he said:

"There was a bug in the code - it used an old rarely supported PHP feature, of turning form fields directly into variables."

He modified the file for me and now it works. So hopefully it will work for you too :)

(only contains the modified file i.e. exportorders.php)

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