After months of discussion with Sony, we regret to say that while we have long been ready to offer mod support on PlayStation 4, Sony has informed us they will not approve user mods the way they should work: where users can do anything they want for either Fallout 4 or Skyrim Special Edition.
Like you, we are disappointed by Sony’s decision given the considerable time and effort we have put into this project, and the amount of time our fans have waited for mod support to arrive. We consider this an important initiative and we hope to find other ways user mods can be available for our PlayStation audience. However, until Sony will allow us to offer proper mod support for PS4, that content for Fallout 4 and Skyrim on PlayStation 4 will not be available.
We will provide an update if and when this situation changes.
Apparently this could be the issue or part of the issue
FYI, these were the reasons brought up a few months ago when they said mods would be delayed:
"KNOWN ISSUES WITH PS4 MODS
PC textures are used. Memory and performance issues may occur. We are working with Sony on optimal texture exporting support in a future update.
Sound files are currently not supported. PS4 sound format is a proprietary format. We are working with Sony on sound file processing support in a future update.
PS4 Mod Storage limit is approximately 900 MB at present. Please do not upload mods larger than 900 MB. We are working with Sony to increase this limit."