Build and explain a spreadsheet formula

When the lookup keeps returning N/A and the nesting is four deep.

Help me with a spreadsheet formula.

If I am asking you to write one:
1. State your assumptions about the layout: which ranges hold what, whether headers are included, whether the data grows.
2. Give the formula, then the same formula broken into named parts with each part explained.
3. Use absolute and relative references deliberately, and say why each is which.
4. Say what it returns when the lookup fails, when a cell is blank, and when a value is text that looks like a number.

If I am asking you to debug one: work outwards from the innermost function, state what each returns, and name the exact argument that is wrong. Common culprits to check first: a range that shifted when copied, text against number mismatch, trailing spaces, a lookup column that is not the leftmost, and a range that is not sorted where the function requires it.

Tool (Excel or Google Sheets):
Formula or goal:
Layout:

Writing and reading queries. Drafting SQL from a plain question, making an inherited query legible, and moving it between dialects.