Try replacing AND with multiplication:

=ArrayFormula(IFS(
    D8:8<1,"",
    (D8:8>0)*(D8:8<=30),D8:8*Tariff!$B3+Tariff!$C3
  ))

The problem is with AND because it checks the entire range and returns a single result (TRUE or FALSE) instead of a range.

=IFS(A1> ( SUM(A3,10), "▲")

You put an extra parenthesis and it shouldn't have been there :)

Try:

=IF(A1>SUM(A3,10), "▲",)

Off the top of my head, this should do what you're looking for.

=IF(A1=1,100,IF(A1=4,200,IF(A1=6,300,IF(A1=10,400,0))))

Broken down into pseudo code:

IF 
  A1=1
THEN
  100
ELSE
  IF 
    A1=4
  THEN
    200
  ELSE
    IF
      A1=6
    THEN
      300
    ELSE
      IF
        A1=10
      THEN
        400
      ELSE
        0

To do it with IFS, this should do:

=IFS(A1=1, 100, A1=4, 200, A1=6, 300, A1=10, 400, true, 0)

SWITCH would be this:

=SWITCH(A1, 1, 100, 4, 200, 6, 300, 10, 400, 0)

Google Sheets functions:

• IF()
• IFS()
• SWITCH()

The double inequality statements aren't valid Sheets syntax. You can simply use =IFS(E2<=45,2,E2<=65,3,E2<=80,4,E2<=100,5,E2>100,"Wrong input"). The IFS() function tests each statement consecutively until it lands on one that is TRUE. If E2<=45 is false, for example, then by necessity E2>45 and so on.

ISNA is most likely what you are wanting, though ISERR or ISERROR could also be applicable depending on the situation.

A couple notes:

• I duplicated your original sheet (see the "Fixes" tab on your Google Spreadsheet), and tightened up the layout slightly so I could better understand what you're trying to accomplish.
• I'm using named ranges in your formula for the tables now, instead of absolute A1 notation ranges. They are easier to maintain, less error prone, and less confusion when writing formulas.
• I removed the timevalue(...) * 24 you were using to convert the formatted DateTime strings to TimeSpans. Instead, I set that column format to TimeSpan (h:mm), which does exactly the same thing without cluttering our formulas.
• "Formula", "Cell 1", and "Cell 2" I separated into columns, so that you and I could test and verify the formula on multiple variations of the cell values at once. The 8 rows you see now are 8 variations of cell 1 and cell 2 ("Formula" column is the same same for all test rows).

The updated working formula is below, based on my best interpretation of your description.

=IF(
COUNTIF(table1, B1), 
INDEX(table3, MATCH(C1, table2, 0)), 
INDEX(table3, MATCH(B1, table2, 0)))

As seen in the help popup in the image below, an IF statement evaluates the first argument (logical_expresion), which must be a value that can be converted into a boolean value (true/false).

Since numbers can represent a bool value (0 = false, anything else = true), and all we need for the first argument is a yes/no, I replaced the first MATCH function with a simple COUNTIF, which simply returns the number of cells in table1 that match B1. Unlike the MATCH function, which returns N/A if no matches are found, COUNTIF simply returns a 0. Since 0 is the same as false, our IF statement knows to use our second MATCH instead of the first.

Note regarding my original answer: The first solution I provided used ISNA(MATCH(...)) = false instead of COUNTIF(...). This works also, but is unnecessarily complicated: ISNA returns true if the value of it's argument is "N/A", true otherwise, effectively converting our MATCH into a bool value. That bool value had to be inverted, however, so that "N/A" value would be false, and a successful match would be true. =false was just used to return the opposite value that ISNA gave us. Does false=false? yes, so we return true. Does true=false? no, so we return...false.

You don't need any if, because iferror already contains an if statement in its logic (as its name suggests). Here is an example of nested iferror statements, simplified for clarity:

=iferror(match("a", A1:A5, 0), iferror(match("a", B1:B5", 0), "not found"))

This will return the position of "a" in column A, if it's there; otherwise, it will return its position in column B if it's there, otherwise it returns "not found".

Works the same with index or anything else around match function.