The Upload script functionality is throwing an error "Script upload failed. Error: Object reference not set to an instance of an object " when trying to upload the script thru ALM-PC UI.
Patch 18 was installed on top of ALM 11 and the relevant ALM client was downloaded on PC server. Upon running the System Health check, the issue was identified as OTA Client version mismatch. The PC server has OTA client related to patch 18 and the PC Host has OTA client related to patch 10.
Run the ALM Client uninstaller on PC server. The utility can be downloaded from KM1400068. Re run the System Health check after ALM client is uninstalled from PC server. This should fix the script upload issue.