Works without premium addons, but not with them

I installed this on my development site yesterday, linked it to dropbox, and did a backup. It worked fine but I could see the zip functionality would be necessary.

So today I installed it on the production server and ordered the bundle. However it doesn’t work. It’s not backing up anything and it’s not throwing an error. As long as I stay on the backup monitor page the button reads Stop Backup. But if I leave and return there is no sign a backup ran at all. There is nothing in dropbox and nothing in the backups folder.

I’m running IIS 7.5. (yeah, I know… not my decision)

https://www.ads-software.com/plugins/wordpress-backup-to-dropbox/