Do you have the latest build of Archicad 25?
As in build 4013?
Maybe that is the problem.
I believe this is acting as a completely new version of Archicad.
Build 4013 can open older build 25 files, but the old builds of 25 can not open the new build files - just like version 24 can not open version 25 files.
Therefore the Datasmith add-on may need to be re-compiled to suit the latest build of 25 - just like it had to be re-compiled when we changed from 24 to 25.
Effectively we have changed versions from 25.1 to 25.2
I might be wrong, but that is my hunch.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10