Trouble with Relation Manager for Many-to-Many Relationship

class KiidPdfPattern extends Model
{
    use HasFactory;

    public $timestamps = false;

    protected $table = 'kiid_dati_tipo';
    protected $primaryKey = 'lunivid';
    protected $guarded = [];

    public function kiidMailPdfs(): BelongsToMany
    {
        return $this->belongsToMany(KiidMailPdf::class, 'kiid_mail_pdf_kiid_dati_tipo', 'kiid_dati_tipo_lunivid', 'kiid_mail_pdf_lunivid');
    }
}

class KiidMailPdf extends Model
{
    use HasFactory;

    protected $table = 'kiid_mail_pdf';
    //protected $connection = 'palliauto';

    public $timestamps = false;
    
    protected $primaryKey = 'lunivid';
    protected $guarded = [];

    public function kiidPdfPatterns(): BelongsToMany
    {
        return $this->belongsToMany(KiidPdfPattern::class, 'kiid_mail_pdf_kiid_dati_tipo', 'kiid_mail_pdf_lunivid', 'kiid_dati_tipo_lunivid');
    } 
}