file.Swift

let headerRefreshTrigger = PublishSubject<Void>()
let retryRefreshTrigger = PublishSubject<Void>()

let refresh = Observable.of(Observable.just(()), headerRefreshTrigger, retryRefreshTrigger.mapToVoid()).merge()
let input = ViewModel.Input(headerRefresh: refresh)

//triggered when retry button tapped
xbutton?.rx.tap.asDriver().drive(onNext: { [weak self] (_) in
            self?.retryRefreshTrigger.onNext(())
 }).disposed(by: rx.disposeBag) 

// Monitor tap action
 retryRefreshTrigger.subscribe {[weak self] _ in
            print("retryRefreshTrigger") 
   }.disposed(by: rx.disposeBag)
//

ViewModel
    struct Input {
        let headerRefresh: Observable<Void>
    }
//Perform Network request
  input.headerRefresh.flatMap({ [weak self] () ->
            Observable<[CellViewModel]> in
            guard let self = self else { return Observable.just([]) }
            self.page = 1
            return self.request()
                .trackActivity(self.headerLoading)
        })
            .subscribe(onNext: { (items) in
                elements.accept(items)
            }).disposed(by: rx.disposeBag)