IF with text and numbers

OK, so first let's talk about the syntax first

What works for you is this:

IF ( VALUE ( 'PowerBI'[SLA Alert] ) > 2,, 1,, 1 )

the thing is '2,' is atually the same as '2.' for me, or how '2,0' would be for you

IF ( VALUE ( 'PowerBI'[SLA Alert] ) > 2,, 1,, 1 )

the red commas are a decimal separator, the blue ones are list separator. That's why this should work as well:

IF ( VALUE ( 'PowerBI'[SLA Alert] ) > 2,0, 1,0, 1 )

As you use modified English settings, I'd suggest using the default option for decimal - the dot '.' and comma as list separator

now the logical problem with this IF (I will use '.' as decimal separator to make it more clear)

IF ( VALUE ( 'PowerBI'[SLA Alert] ) > 2., 1., 1 )

it returns '1.' for TRUE and '1' for FALSE. Which is always 1 with whatever is the formatting in your column. You need to change one of the '1' to something that you want to see, like I posted earlier:

Test = IF (
    ISBLANK ( PowerBI[DueBy] ),
    BLANK (),
    IF (
        ISERROR ( VALUE ( PowerBI[SLA Alert] ) ),
        BLANK (),
        IF ( VALUE ( 'PowerBI'[SLA Alert] ) > 2 , 2 , 1 )
    )
)

'2' for TRUE and '1' for FALSE