Is the packaging of all the packages successful.
When the packaging of one of the packages is failed with errors (see below image) and we try to accept the delivery, the delivery cannot be accepted as the Delivery is incomplete.
If one or more packages content state is "Not packaged".
The solution is to cleanup the Deployment folder(Check if anything is deployed from that application->If Yes,cleanup the deployment folder of that application),then package the application by selecting "Force extraction" option and "Entire Version".After packaging is successful for entire version,deliver the application and in CAST-MS,accept the delivery.
Also this issue may be because of few operating system files which are present while packaging the source but not when accepting the delivery. See Delivery Manager Tool - Information - File Types and folders which can be ignored to understand the file types which should/can be ignored while packaging. The page would give you the details of the files which are not part of the analysis yet present in the source code and which may effect the packaging process, disk space and the memory while packaging.