Not very much sure but Well, as per description by Microsoft, the total length of ReportServerURL+ReportName should not exceed 260 chars
in addition your report name must not be using any special chars
I would recommend you to re-run All Reports deploy command, and as error comes, don't close window. notE down error message, with care, and note that if ReportServerURL+ReportName is more than 260
when report deployment fails in AX, it always gives you name of report where it fails