you are using AND WHERE condition, I instead you can use OrWhere

I see 2 options to interpreter your question. The first is like @suhailparad metioned with an orWhere that means one of the criteria need to match.

It reads like: if year == selectedyear OR cell = selectedDepartment ...

$hours = Sap_cm01::join('production_supervisors', 'production_scheduler', '=', 'pr_superv')
    ->orWhere('year', $selectedYear)
    ->orWhere('cell', $selectedDepartment)
    ->orWhere('area', $selectedValueStream)
    ->orWhere('sap_cm01.ap', $apData)
    ->sum('val');
dd($hours);

The second way is how I read it. It can happen that not al the criteria are provided. Here is the when option useful (see: https://laravel.com/docs/8.x/queries#conditional-clauses )

It reads like: if year is provided then year == selectedyear AND if department is provided cell = selectedDepartment ...

$hours = Sap_cm01::join('production_supervisors', 'production_scheduler', '=', 'pr_superv')
    ->when($selectedYear, static function (Builder $yearQuery, $selectedYear): void {
        $yearQuery->where('year', $selectedYear)
    })
    ->when($selectedDepartment, static function (Builder $departmentQuery, $selectedDepartment): void {
        $departmentQuery->where('cell', $selectedYear)
    })
    ->when($selectedValueStream, static function (Builder $valueStreamQuery, $selectedValueStream): void {
        $valueStreamQuery->where('year', $selectedValueStream)
    })
    ->when($apData, static function (Builder $apDataQuery, $apData): void {
        $apDataQuery->where('sap_cm01.ap', $apData)
    })
    ->sum('val');
dd($hours);

I hope this can help you :)