If you are riding on Alp du Zwift before you enter into an event, once you join that event, the rider list will continue to be the small version of the rider list that is shown on the Alp, and the mini map will not be displayed.
Thanks for reporting this issue. Could you please ensure that both Zwift and Zwift Companion(if you use it) are using the most recent versions. Once you have your apps up to date, please try to replicate this issue. If you do successfully replicate this issue, please take another screenshot and submit a support ticket here. Once we receive your ticket we’ll gladly help you troubleshoot this issue.