The collection link you generate from the app (anything that looks like www.getpostman.com/collections/<unique id>) can only be updated by the creator of the collection.
If you need a collection link to be updated by team members, you can use the Pro API (https://api.postman.com). This will give you a URL that always returns the up-to-date version of the collection from our Sync system. Any change made to this collection by you or by any of the subscribers in your team will be instantly reflected at the Pro API URL.
Documentation about the Pro API can be found here