Switch Statement is not Working

HI heygowtam.

I'd like to suggest you try to use the following calculated column formula with logic operators instead of DATESBETWEEN function:

Leaves =
SWITCH (
    TRUE (),
    [Start date] <= DATE ( 2022, 07, 01 ),
        IF (
            [Employment Type] = "Full Time",
            20,
            IF ( [Employment Type] = "Part Time", 12 )
        ),
    [Start date] > DATE ( 2022, 07, 01 )
        && [Start date] <= DATE ( 2022, 08, 01 ),
        IF (
            [Employment Type] = "Full Time",
            20,
            IF ( [Employment Type] = "Part Time", 12 )
        ),
    [Start date] > DATE ( 2022, 08, 01 )
        && [Start date] <= DATE ( 2022, 09, 01 ),
        IF (
            [Employment Type] = "Full Time",
            18.37,
            IF ( [Employment Type] = "Part Time", 11 )
        ),
    [Start date] > DATE ( 2022, 09, 01 )
        && [Start date] <= DATE ( 2022, 10, 01 ),
        IF (
            [Employment Type] = "Full Time",
            16.70,
            IF ( [Employment Type] = "Part Time", 10 )
        ),
    [Start date] > DATE ( 2022, 10, 01 )
        && [Start date] <= DATE ( 2022, 11, 01 ),
        IF (
            [Employment Type] = "Full Time",
            15,
            IF ( [Employment Type] = "Part Time", 9 )
        ),
    [Start date] > DATE ( 2022, 11, 01 )
        && [Start date] <= DATE ( 2022, 12, 01 ),
        IF (
            [Employment Type] = "Full Time",
            13.36,
            IF ( [Employment Type] = "Part Time", 8 )
        ),
    [Start date] > DATE ( 2022, 12, 01 )
        && [Start date] <= DATE ( 2023, 01, 01 ),
        IF (
            [Employment Type] = "Full Time",
            11.7,
            IF ( [Employment Type] = "Part Time", 7 )
        ),
    [Start date] > DATE ( 2023, 01, 01 )
        && [Start date] <= DATE ( 2023, 02, 01 ),
        IF (
            [Employment Type] = "Full Time",
            10,
            IF ( [Employment Type] = "Part Time", 6 )
        ),
    [Start date] > DATE ( 2023, 02, 01 )
        && [Start date] <= DATE ( 2023, 03, 01 ),
        IF (
            [Employment Type] = "Full Time",
            8.35,
            IF ( [Employment Type] = "Part Time", 5 )
        ),
    [Start date] > DATE ( 2023, 03, 01 )
        && [Start date] <= DATE ( 2023, 04, 01 ),
        IF (
            [Employment Type] = "Full Time",
            6.68,
            IF ( [Employment Type] = "Part Time", 4 )
        ),
    [Start date] > DATE ( 2023, 04, 01 )
        && [Start date] <= DATE ( 2023, 05, 01 ),
        IF (
            [Employment Type] = "Full Time",
            5,
            IF ( [Employment Type] = "Part Time", 3 )
        ),
    [Start date] > DATE ( 2023, 05, 01 )
        && [Start date] <= DATE ( 2023, 06, 01 ),
        IF (
            [Employment Type] = "Full Time",
            3.34,
            IF ( [Employment Type] = "Part Time", 2 )
        ),
    [Start date] > DATE ( 2023, 06, 01 )
        && [Start date] <= DATE ( 2023, 07, 01 ),
        IF (
            [Employment Type] = "Full Time",
            14.67,
            IF ( [Employment Type] = "Part Time", 1 )
        )
)

Regards,

Xiaoxin Sheng