“Couldn't send a valid signature” error when using CloudKit without iCloud account

Question

I have submitted an iOS app that uses CloudKit to Apple. It's being rejected because it requires user to sign into iCloud for access. Apple's reasoning is that even without iCloud sign-in, the public database is still readable. So that part of the app should function.

I am trying to modify the app but I continue to get this error when I am not signed in.

<CKError 0x8141a360: "Internal Error" (1/4000); "Couldn't send a valid signature">

I have searched the web and the solution is always just to sign into iCloud. There is no Apple documentation regarding this error either. Does anyone know how to resolve this without signing into an iCloud account? Thank you very much.

Answer 1

I had the same error but a slightly different cause, so for this problem another thing to check (other than that @Cakelly posted themselves as a comment):

This error can also occur if you try to access the Production database from the simulator, even if you are signed in to iCloud. Change back to the Development database to test on a simulator.