constant contact feed stopped

i have a form that has feeds to 2 separate constant contact lists. it’s been working for a few weeks, but one of the 2 stopped working. no amount of fiddling (deleting/adding feed, feeding from a new field, exporting/importing the whole form, duplicating form) fixes the one feed, but the other keeps on working.

on a brand new form, the feed in question works just fine.

how do i troubleshoot this?

https://wordpress.org/plugins/gravity-forms-constant-contact/