Please check the following points:
The Mission Completion SBT can be obtained only after downloading all the required apps.
Once the mission is completed, a message stating that the Mission Completion SBT is available will be sent to the "Notifications" section (bell icon at the top right) of the Digital Wallet. Tap "Get the Mission Completion SBT" in the message to claim it.
If you are still unable to obtain it after following the above steps, go to the Digital Wallet home screen > "Connect" tab > "Events & Services" list, select the relevant event or service, and tap the "?" icon on the "Mission Completed" stamp to move to the acquisition screen and receive the SBT.