This issue occurs due to residual files left in the APPData that need to be deleted.


Step 1: Please uninstall LG mail viewer via Add or Remove Programs.

Click the uninstall button below:
Step 2: On your Cloud, press Windows + R and paste the text below into the 'Run' text box.
%localappdata% 

Then click 'OK'


Step 3: Then delete the 2 folders below:


Step 4: Copy and install the latest MailViewer app which is found here:
S:\25. LGEAP\New 25.LGEAP\1.Software\2.LG\LG Mailviewer Setup


Kind Regards,