Same problem here with 26.1 I have complete wild guess: The issue may originate from iCloud-Apple-whatever-enforced constraints within the local filesystem sandbox or from misconfigurations in the iCloud container provisioning layer or failures in the underlying iCloud service endpoints responsible for file coordination and metadata synchronization. Alternatively, the root cause could be an incomplete or corrupted code-signing pipeline within Xcode or the like. In addition, a failed or skipped notarization step, an unprocessed staple operation, or an artifact that was signed outside the expected keychain context can prevent the resulting binary from passing Apple’s runtime validation, ultimately blocking proper initialization. It has perhaps its root cause in the new (ugly and power lavishing 2007ish Windows Vista Aero designed) OS. Perhaps it's so complicated to fix, that this app is beyond (costly) repair. Best regards, S.

Late to the party. Nonetheless, an even simpler solution was to "Clean" the project from Product-->Clean Build Folder. After that I checked my Certificate as described in the previous posts. All was fine with it, as I believe, so why an issue at build time? That final step was to run "Build". That's it. Coming from a IntelliJ IDEA, Vi, VSCode, awk, sed, Shellscript and Linux World and Java as my main language, I don't get the hassle Apple creates with its Signing stuff. Why would someone at an early stage of development need that? I do that at the end before shipping by random, here its mandatory. Just why? The problem I want to mark is, that, when I close my working cheap project with some Metal, 3D stuff and change nothing, then re-open it a week later and just fire it up, why does this strange Xcode thing keeps me bugging me with "Command CodeSign failed with a nonzero exit code"?