More details can be found in this bug filed on Github:
“The DDB Importer module shows up in manage modules as installed, but it does not show up in configure settings and does not show as a button on the player character sheet when in edit mode.”
The module maintainer, Mr. Primate, said this is likely due to the way Forge installs modules, but I’m not sure if there is some way to get this working again. I haven’t had any issues using the standard Foundry module install route until this version.