SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`seller`.`sellers`, CONSTRAINT `sellers_user_id_foreign` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE)

please how do i resolve this issue , the user table is in another database different from the seller database

SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`seller`.`sellers`, CONSTRAINT `sellers_user_id_foreign` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE)

my livewire

 $user = User::where('email', $this->email)->first();

        if (!$user) {
            // $studentNumber = $this->generateUniqueStudentNumber();

        
            $user = User::on('second_db')->create([
                'name' => $this->name,
                
                'email' => $this->email,
                'password' => bcrypt($this->password), // Correctly hash the password
            ]);
        }
        

        if (!$this->isStudent) {
            $this->validate([
                'nin' => 'required',
                'state' => 'required',
                'picture' => 'required|image',
            ]);
        } else {
            $this->validate([
                'department' => 'required',
                'schoolIdCard' => 'required|image',
            ]);
        }

       

        // Upload school ID card image
        if ($this->isStudent) {
            $schoolIdCardPath = $this->schoolIdCard->store('public/school_id_cards');
        } else {
            $picturePath = $this->picture->store('public/seller_pictures');
            $schoolIdCardPath = null;
        }


        // Save seller to the database
        // Seller::create([
        //     'user_id' => $user->id,
        //     'is_student' => $this->isStudent,
        //     'department' => $this->department,
        //     'school' => $this->school,
        //     'school_id_card' => $schoolIdCardPath,
        //     'picture' => $picturePath,
        //     'state_id' => $this->state,
        //     'business_name' => $this->business,
        //     'nin' => $this->nin,
        //     'address' => $this->address,
        //     'whatsapp_number' => $this->whatsappNumber,
        //     'verification_status' => false,
        // ]);

        $seller = new Seller();
        $seller->setAttribute('user_id', $user->id);
        $seller->setAttribute('state_id', $this->state);
        $seller->is_student = $this->isStudent;
        $seller->department = $this->department;
        $seller->school = $this->school;
        $seller->school_id_card = $schoolIdCardPath;
        $seller->picture = $picturePath;
       
        $seller->business_name = $this->business;
        $seller->nin = $this->nin;
        $seller->address = $this->address;
        $seller->whatsapp_number = $this->whatsappNumber;
        $seller->verification_status = 0;
        $seller->save();

my model

class Seller extends Model
{
    use HasFactory;
    protected $connection = 'mysql';
    protected $guarded = [];
   


    public function user()
    {
        return $this->belongsTo(User::class);
    }
}