If you are using an external IMSS Database which is connected via FQDN then it can happen that you see this error message:
Please check if you see these informations in the /opt/trend/imss/UI/ROOT/log/AdminUIDebugLog
14:14:47,041 - ERROR debug - ERROR: could not open server file "/tmp/patchupload/EULA.txt": No such file or directory [com.trendmicro.imss.ui.modelobjects.system.PatchInfoDAO.writePatchInfo(PatchInfoDAO.java:102)] 15:38:49,238 - ERROR debug - Unable to export the End User License Agreement file. Re-download the file and try again. If the problem persists, restart IMSVA. [com.trendmicro.imss.ui.system.PatchAction.view(PatchAction.java:808)]
If you see this information in the Logs please install Critical Patch 1623 to fix this issue. Afterwards you will be able to install the Hotfixes and Patches.