The account could not be able to load the collections app page, the request api/catalog_system/pvt/collection/search/?an=&page=1&pageSize=10&orderByAsc=false could return 500, due to timeout:

"Execution Timeout Expired. The timeout period elapsed prior to completion of the operation or the server is not responding."

• Go to /admin/collections

• Manage collections using legacy CMS or using API.