Since UE 5.4 and 5.5 are working as intended, the error you are receiving aims at a compatibility issue between UE5.6 and the MSVC toolchain.
Now, just to make sure this is not simply corruption due engine migration, the first step would be a cache clear. Please close UE, go to your project directory, and delete folders Binaries/, Intermediate/, Saved/, and .vs/, then regenerate your project files from VS, and re-open UE.
The next step, is to make sure that your UE and VS setup is properly configured, and that all installed elements have the correct version. You can review this process with the documentation below:
Finally, in Rider, open Settings > Toolchains, and manually set the paths for your MSVC and SDK. After that, try to compile again. Hope this helps!
im on 5.5, my project packaged just fine last weekend, now i come back and after windows update, try to package same error as you get “UAT: [27/28] Link [x64] game_name.exe
[2025.07.18-02.12.59:638][318]LogPlayLevel: UAT: LINK : fatal error LNK1123: failure during conversion to COFF: file invalid or corrupt”.
i have tried re installing visual studio, all sdks, all MCVCs, all .NET frameworks, cleared project Intermediate, Binaries, Saved. regenerated, cleaned, rebuild and fetched from github, tried earlier commits.. and so on.. it builds fine on visual studio but when i try to package in unreal this happens. losing my mind here.