[Membership 2 Pro] Membership2 API Not Working

Having same issue as other threads. /wp-json/membership2/v1?pass_key={MYKEY} returns JSON, but any other endpoint returns 404. I swapped the api file for the one attached to the first reply of https://premium.wpmudev.org/forums/topic/how-do-i-use-membership-2-pro-rest-api-add-on , however updating the entire plugin to a beta version offered in that thread on a live site makes me nervous. Especially seeing that my version is 1.1.5.

The end of this issue is I am trying to setup an endpoint that my client's internal membership system can pull all members and their data, much like the export function does but through the API.