If you were able to see some reports on the Reports list, but they are not there now, it could be because some of your subscription packages have expired. Each subscription package in Core includes a defined set of reports. If one of your subscriptions expires, the reports unique to it are no longer visible in the Reports screen. It could also be because your report permissions were changed by the Core Administrator. You can regain access to the reports by renewing the expired subscriptions or checking with your Core Admin. Check out this article that lists the reports included in each subscription package: Core reports by subscription packages.