Something isn't working correctly to generate the .xml file or add any data to it.
I removed the extensions and reinstalled the new build.
Then I created a new map. All new page and files were generated. It didn't create the _promaps_cache folder or the _promaps_geocache.xml file. So I created the directory with (755 permissions) and the file with (644) and uploaded them.
Still no data added.
So I then added the xml tags to the file.
<?xml version="1.0" encoding="UTF-8"?>
Again nothing. Something is preventing it from creating the file and nothing will write to it once it's created manually. Not sure why.
I have not tried to delete the xml file from the test site you worked on, to see if it would be regenerated. Should I?