This may depend on the version of DIA-NN you are using. Skyline still depends on an older version (version 3) of the .speclib format, while DIA-NN has moved on to newer formats. DIA-NN has implemented a way to export format version 3 compatible .speclib files for Skyline which are generally named .skyline.speclib, but I am not clear on whether this is possible for the .predicted.speclib (i.e. if you can get a .skyline.predicted.speclib).
I will check with Vadim on this. Have you tried it and gotten an error? If so, can you post the error?
Thanks for posting this issue to the Skyline support board.
--Brendan