Uzywam next-auth do logowania. Na localhost:3000 wszystko dziala natomiast na codesandbox.io otrzymuje błąd.
https://ngjvt6-3000.csb.app/api/auth/signin?csrf=true i pozniejsze logowanie z Credentials takze nie dziala logowanie z
tutaj jest moje repozytorium:

https://codesandbox.io/p/github/arturnowakowski2015/nextapps/main

tak wyglada moj provider:

const handler = NextAuth({
  providers: [
    CredentialsProvider({
      name: "Credentials",
      credentials: {
        username: { label: "Username", type: "text", placeholder: "Username" },
        password: { label: "Password", type: "password" },
      },
      async authorize(credentials, req) {
 
        const user = await res.json()
         alert(credentials);  ///to wogole sie nie wywoluje

        try {
          const user = User.filter((t) => {
            return t.email === credentials.email && t;
          })[0];
           if (user) {
            const isPasswordCorrect = await bcrypt.compare(
              credentials.password,
              user.password
            );
         
            if (isPasswordCorrect) {
              return user;
            } else {
        

              throw new Error("Wrong Credentials!");
            }
          } else {
            throw new Error("User not found!");
          }
        } catch (err) {
          throw new Error(err);
        }
      },
    }),
 
  ],
  pages: { error: "/dashboard/login" },  session: {
     strategy: 'jwt'
  }
});