VBA behaving weirdly, can't get the value stored in variable - excel

Question

I am having a very strange problem. I am not able to get the value returned from a simple function as below if the return value is more than one char. Now the second problem is that following code is not assigning "WTH" to sheetName variable. Refer to the screenshot 2. UPDATED AFTER CYRIL'S COMMENTS
Public Sub WTHFormatter()
Dim sheetName As String
sheetName = "WTH"
Dim rng1 As Range
'delete empty rows
lastRowWTH = getLastRow(sheetName, 2)
'Delete rows below the last Row
Worksheets(sheetName).Rows(lastRowWTH + 1 & ":" & Worksheets(sheetName).Rows.Count).Delete
' build first range
Set rng1 = Worksheets(sheetName).Range("B11:F" & lastRowWTH)
Call setCellBorders(rng1)
Set rng1 = Worksheets(sheetName).Range("H11:K" & lastRowWTH)
Call setCellBorders(rng1)
'determine the range for months
For i = 13 To 24
If Cells(7, i) = "" Then
lastCol = i - 1
Exit For
End If
lastCol = i
Next
ColLetter = returnLabel(lastCol)
ColLetter2 = returnLabel(lastCol + 2)
ColLetterX = returnLabel(lastCol + 14)
Set rng1 = Worksheets(sheetName).Range("K17:" & ColLetter & lastRowWTH)
Call setCellBorders(rng1)
Set rng1 = Worksheets(sheetName).Range(ColLetter2 & lastRowWTH & ":" & ColLetter3 & lastRowWTH)
Call setCellBorders(rng1)
End Sub
Function returnLabel(num1 As Long) As String
Dim ColumnLetter As String
ColumnLetter = Split(Cells(1, num1).Address, "$")(1)
returnLabel = ColumnLetter
End Function
The above function returns blank and varTest has nothing after the execution. If I do the line by line execution, I see that test1 in function is not 'Null'.
If I break the execution and probe the variables I see "test1 =" only as per the screen shot below. And this is breaking my code.
Strangely, If I call the function from 'Immediate Window', it returns the expected value.
Things I have already done:
I have tested in a fresh file using simple code as above.
Tested in different PC and the same code is working fine with same version of Windows 10 & Office 365.
Updated / Re-installed MS Office 365
Restarted the PC
If the return value is a single character like "A", the code is working fine.
Failed to understand the reason here. Any help is appreciated.
UPDATE1
I tried it on a fresh file while the code above worked, but the main code is having a new similar problem. This has started happening just now. It's not assigning a string value to the variable. See the attached screenshot.Screenshot of the VBA Code. I am assuming there is some problem with system or some virus.

Answer 1

If the idea is to have a function, that an array, this is possible with the following code:
Function Test1() As Variant
ReDim result(2)
result(0) = "AJ"
result(1) = "A"
Test1 = result
End Function
Sub Main()
Dim varTest As Variant
varTest = Test1(0)
Debug.Print varTest
varTest = Test1(1)
Debug.Print varTest
End Sub
It is questionable why would it be needed, but as a "test-exercise" it is ok.

Answer 2

Going to put my comments into an answer to consolidate and add more explanation.
Pointing out some errors in the code before correcting:
Function test1(num1) 'declare `as variant` to ensure you're returning an array
test1 = "AJ" 'this appears to be saving a single string to var test1
test1 = "A" 'you are now overwriting the above string
End function
Sub test()
varTest = test1(1) 'you have a single string from the function and arrays start at 0, not 1
End sub
You would want to specify the place in the array, after declaring an array, within your function such that:
Function test1() As Variant
Dim arr(2) As Variant 'added array because test1 = BLAH is the final output in a function
arr(0) = "AJ" 'added (1) to call location in array
arr(1) = "A" 'added (2) to call location in array
test1 = arr
End Function
Sub test()
Dim varTest As Variant
varTest = test1(0) 'outputs "AJ" in immediate window
Debug.Print varTest
End Sub
Now you can debug.print your array values, or set to varTest based on the location in the array.
Edit: Tested after my consolidating comments and recognized that there was not an actual output for test1 as an array at the end of the function, so had to go back and add a second array to set test = allowing an array output from a function.

Answer 3

Your code is running as it should.
The test1 function assigns the value AJ to the test1 variable, and then it assigns the value A to the test1 variable.
You could assign the value 50 in your test procedure and it will return A.
I think this is the code you're after:
Function test1(num1) As String
' Dim MyArray As Variant
' MyArray = Array("AJ", "A")
'OR
Dim MyArray(0 To 1)
MyArray(0) = "AJ"
MyArray(1) = "A"
If num1 >= LBound(MyArray) And num1 <= UBound(MyArray) Then
test1 = MyArray(num1)
Else
test1 = "Item not here"
End If
End Function
Sub test()
Dim varTest As String
'Return the second item in the array from the function.
varTest = test1(1)
MsgBox varTest
'Return the first item in the array from the function.
varTest = test1(0)
MsgBox varTest
'Returns "subscript out of range" error as array is only 2 elements in size (0 and 1).
'The error is dealt with in the function using the IF....ELSE...END IF block and returns
'"Item not here" instead.
varTest = test1(2)
MsgBox varTest
End Sub

Answer 4

I solved this by using declaring the variables even when option explicit is not used.
The old code runs without throwing errors even when the variable is not declared and option explicit is also not used. But, for some reasons, it doesn't read / write undeclared variables as expected.
Now as per #cyril suggestion, I declared the variables being used and run the code. This time code ran as expected.
This happened for multiple of variables and at different stages in the code.