Which service were you using to send the zap?
While using Primal, I tried to zap nostr:npub19xgymswuxyq4sx58enft9c6algrm72a6lchplm4rjzgklufn9ygq5kcu58 and nostr:npub12rzunrxvx89f78h4df284lzvkjqetljkq0200p62ygwmjevx0j8qhehrv9 and it failed. 6 days ago
The other way around I forget who exactly. But it was someone with a primal address and I was using my getalby address.