Change column values based on different column values

The structure/syntax of the step looks fine. Is it perhaps just a typo: [Customers] instead of [Customer]?

This test query appears to work as intended:

let
  Source = #table(
    type table [Date = date, Customer = text, Industry = text],
    {
      {#date(2025, 1, 5), "A", "Aerospace"},
      {#date(2025, 1, 10), "B", "Baking"},
      {#date(2025, 1, 15), "C", "Carpentry"},
      {#date(2025, 1, 20), "B", "Baking"},
      {#date(2025, 1, 25), "B", "NA"},
      {#date(2025, 1, 30), "D", "Detailing"},
      {#date(2025, 2, 4), "A", "NA"}
    }
  ),
  #"Replace Values" = Table.ReplaceValue(
    Source,
    each [Industry],
    each
      if [Customer] = "A" then "Aerospace"
      else if [Customer] = "B" then "Baking"
      else if [Customer] = "C" then "Carpentry"
      else if [Customer] = "D" then "Detailing"
      else [Industry],
    Replacer.ReplaceText,
    {"Industry"}
  )
in
  #"Replace Values"

Hi mikesdunbar,
Thank you for reaching out to the Microsoft Fabric Community Forum.

I have reproduced your scenario in Power BI using Power Query and was able to achieve the expected outcome as per your requirement. For your reference, I’m attaching a .pbix file so you can explore the complete steps directly.

Output:

Thanks you, OwenAuger for sharing your valuable insights.

If this information is helpful, please “Accept as solution” and give a "kudos" to assist other community members in resolving similar issues more efficiently.
Thank you.