i can't create my iCloud account on my mac

Maximum limit for creating Apple ID from the hardware address of Mac is three , you can't create more Apple ID accounts , however again sign in with your same Apple ID and it's account credentials ( in fact you have signed out the Apple ID ) in the empty fields or sign in with another apple id that was created from another Mac / iPad or different iPhone .

See the article Sign in with your Apple ID - Apple Support

Second possible reason How to delete your Apple ID account - Apple Support

When your Apple ID account is deleted, your account details and the data associated with your Apple ID are permanently deleted from Apple’s servers. You can't sign in to your account, and you won’t be able to access any data, content, or services that were associated with your Apple ID.