We have an internal SSRS site that works correctly however when users try to Export (download) a report as pdf/xls etc. a new tab opens which remains blank. This behaviour was similar in v53 however at this point they would be prompted to save/download and the download would proceed. The report runs in a popup (popups are allowed), and starting in v54 when Export is selected the popup closes which causes the new blank tab in the parent window. In previous versions the popup remains open.