Treat as function not working with variable

Hi Everyone,

I have the following DAX expression my issue is when I use this expression with le variable _Year is returns me a blank when I harcode the period I want example "2021.TOTAL", it is working and I do not understand what is the issue has I check the variable, if it is a text or a case issue but everything is align with what I need, any clue how to fix it ?

Act Previous Years = VAR default_year = YEAR(LASTDATE(ALL(DimDate[Date by Years])))-1

VAR selected_year = YEAR(SELECTEDVALUE('DimDate'[Date by Years]))-1

Var _Year = SWITCH(
    TRUE(),
    ISFILTERED(DimDate[Date by Years]),
    CONCATENATE(CONVERT(selected_year,STRING), ".TOTAL"),
    CONCATENATE(CONVERT(default_year,STRING), ".TOTAL")
)

VAR _Type = "ACTUAL - Actual"

	VAR _Result = CALCULATE(
		[Actual],
		TREATAS(
			{
				_Year
			},
			'Data'[Period Available]
		),
		TREATAS(
			{
				_Type
			},
			'Data'[Type]
		)
	)
	RETURN
		_Result