The same is discussed in other thread -
Document is not getting opening in SAP
Below is my answer from that thread
Reason for the problem:
The document is getting downloaded to the local machine and the system is unable to find the file in the folder path defined in DC20.
Solutions that I found -
1. Search by the file name in your system to figure out the temporary folder where the file is downloaded from SAP Content server (the file path is defined during SAP installation by GUI for the default folder). Place the same folderpath in DC20 txn in R3. You should be able to see the file on double clicking the file in CV02N/CV03N
2. Just remove the folder path in DC20 txn and tick the checkmark for online. The file will be directly opened from the content server.
Thanks