Issues With PowerQuery Using 2 Tables with different Data Sets

Hi

making a stripped down version of your workbook with anonymized information shouldn't take more than 15 mins and without even your query code it's virtually impossible to help

Only thing that comes in my mind given the info. you posted is a mismatch between [Asset Id]s (or [Work Order Id]s - not clear which field(s) you use to merge the tables) in your Tables. They're Text values meaning they could contain trailing space(s) and/or invisible/unprintable char(s) like Unicode Char 160 (often 'included' with copy/paste from the Web)

Query1
Table1 has a couple of those chars (have taken [Asset Id] as ex.):

let
    Table1 = #table( {"Asset Id"},
        {
            {"123"},
            {"456 "},                               // Has trailing space
            {"789" & Character.FromNumber(160)}     // Has trailing unichar 160
        }
    ),
    Table2 = #table( {"Asset Id", "Equipment"},
        {
            {"123", "ABC"},
            {"456", "DEF"},
            {"789", "GHI"}
        }
    ),
    MergedTables = Table.NestedJoin(
        Table1, "Asset Id",
        Table2, "Asset Id",
        "Table2", JoinKind.LeftOuter
    ),
    ExpandedEquipment = Table.ExpandTableColumn( MergedTables, "Table2", {"Equipment"} )
in
    ExpandedEquipment

Query1 result:

Query2
Fixes [Asset Id] on Table1:

let
    Table1 = #table( {"Asset Id"},
        {
            {"123"},
            {"456 "},                               // Has trailing space
            {"789" & Character.FromNumber(160)}     // Has trailing unichar 160
        }
    ),
    CleanedTable1_AssetId = Table.TransformColumns( Table1,
        {"Asset Id", each
            Text.Replace(
                Text.Trim( _ ),                     // Removes trailing space(s)
                Character.FromNumber(160), ""       // Replaces unichar 160 withe 'nothing'
            )
        }
    ),
    Table2 = #table( {"Asset Id", "Equipment"},
        {
            {"123", "ABC"},
            {"456", "DEF"},
            {"789", "GHI"}
        }
    ),
    MergedTables = Table.NestedJoin(
        CleanedTable1_AssetId, "Asset Id",
        Table2, "Asset Id",
        "Table2", JoinKind.LeftOuter
    ),
    ExpandedEquipment = Table.ExpandTableColumn( MergedTables, "Table2", {"Equipment"} )
in
    ExpandedEquipment

Query2 result:

If that doesn't help at all post at least your complete query code please