We faced same issue. From the beginning of September our application bundle couldn't be notarised because of some .jnilib and .dylib was not signed.
We tried notarise our previous release, which was notarised successfully before and got same error.
When I verify signed application it returns it's valid
codesign --deep --verify --strict --verbose=3 Our_App.app
.....
Our_App.app: valid on disk
Our_App.app: satisfies its Designated Requirement
Can you say if it was changes in notarisation process on Apple notarisation service?