Hi @alreadytiredtomorrow, welcome to the Community!
Ah, when selecting the custom value option for a dropdown field you’ll need to enter the ID for the option, not it’s name. You can find out more about that here: Add custom values to dropdown menu fields in Zaps.
That said, should the new subscribers be added to the same segment in Flodesk or is this determined by some value that’s obtained from the Stan app?
If it’s the same every time, is it still erroring when a different segment is selected from the dropdown menu on the Segment field?
If it’s different every time, and the segment is determined by a value the Zap received from Stan, then you’ll likely need to add a Formatter (Utilities > Lookup Table) action to convert that value into the relevant ID for the segment. The segment ID should appear directly under the name of the segment in the list of available segments in the dropdown menu (in the Segment field). Do you think that could work? If so and you’re not familiar with lookup tables you can find out more about them here: Create lookup tables in Zaps
Looking forward to hearing from you on this!