Hello Adam,
The upgrade path for DMM and SNS are dependent on Hardware platform. Not all the hardware platforms can be upgraded to 5.2.3 and beyond.
You can find the Hardware compatibilty information in the release notes of each release.
What is the hardware platform of your DMS deployment? You can find the hardware details, by initiating an SSH to the DMM and SNS and clicking on "Show_INFO"
Thanks,
Sagar Dhanrale