Excel public function no longer works and results in name error when it used to work before restart

Question

In order to use TEXTJOIN in excel 2016, I used this public function in my excel but after restarting my PC I get name error when this function used to work. I created a new module and copied and pasted the text as is

How to replicate Excel's TEXTJOIN function in VBA UDF that allows array inputs

I have to specify the file I am working in and the module and then the function again for it to work. aka =testfile!tjoin.tjoin(function parameters)

Public Function TJoin(Sep As String, ParamArray TxtRng() As Variant) As String
On Error Resume Next
'Sep is the separator, set to "" if you don't want any separator. Separator must be string or single cell, not cell range
'TxtRng is the content you want to join. TxtRng can be string, single cell, cell range or array returned from an array function. Empty content will be ignored
Dim OutStr As String 'the output string
Dim i, j, k, l As Integer 'counters
Dim FinArr(), element As Variant 'the final array and a temporary element when transfering between the two arrays

'Go through each item of TxtRng(),  depending on the item type, transform and put it into FinArray()
i = 0 'the counter for TxtRng
j = 0 'the counter for FinArr
k = 0: l = 0 'the counters for the case of array from Excel array formula
Do While i < UBound(TxtRng) + 1
    If TypeName(TxtRng(i)) = "String" Then 'specified string like "t"
        ReDim Preserve FinArr(0 To j)
        FinArr(j) = "blah"
        FinArr(j) = TxtRng(i)
        j = j + 1
    ElseIf TypeName(TxtRng(i)) = "Range" Then 'single cell or range of cell like A1, A1:A2
        For Each element In TxtRng(i)
            ReDim Preserve FinArr(0 To j)
            FinArr(j) = element
            j = j + 1
        Next
    ElseIf TypeName(TxtRng(i)) = "Variant()" Then 'array returned from an Excel array formula
         For k = LBound(TxtRng(0), 1) To UBound(TxtRng(0), 1)
            For l = LBound(TxtRng(0), 2) To UBound(TxtRng(0), 2)
                ReDim Preserve FinArr(0 To j)
                FinArr(j) = TxtRng(0)(k, l)
                j = j + 1
            Next
         Next
    Else
        TJoin = CVErr(xlErrValue)
        Exit Function
    End If
i = i + 1
Loop

'Put each element of the new array into the join string
For i = LBound(FinArr) To UBound(FinArr)
    If FinArr(i) <> "" Then 'Remove this line if you want to include empty strings
    OutStr = OutStr & FinArr(i) & Sep
    End If
Next
 TJoin = Left(OutStr, Len(OutStr) - Len(Sep)) 'remove the ending separator

End Function