Approval Groups Drop Down Blank

Summary:

I'm working on cleaning up our Workflows because they were set up in a messy way. When I go in to create a new rule, the Approval Groups drop down menu is blank (no options). The Approval Groups are all set up, so that's not an issue. Also, there are existing Workflows and the drop down menu is blank for the Approval Groups too, but the Workflows themselves still work as expected. Approval Groups work as expected in Test. Any ideas on what could be causing the drop down menu to be blank?

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