I can access it opening the links in Getting Started page, but I cannot find report on Project Reports tab in Jira Service Desk Portal or JIra Software Next-Gen project.
In case of Jira Cloud there is system navigation bar and project navigation bar menu item created, which is shown for members of user groups selected in Auditors Groups or Time Entry Issue Panel Groups options or for projects selected in Time Entry Issue Panel Projects option, if any configured in app Configuration accessible using Gear icon from report page or via Jira Settings - Apps - Timesheet or Time Reports Configuration.
Or you can add quick link with Application Navigator (for Jira Server) or Project Shortcuts (for Jira Server) to the reports. The links can be found at the Getting Started page.
Note, report may also be opened using Details link in corresponding Dashboard gadget.