Expression.Error: The index cannot be negative

[Zoru]

Hi All, 

Maybe you can help me with this error. I was running Power Query a lot of times and did not have this error. 

Now it showed up and I am not able to find where is the issue with it. 

An error occurred in the ‘Test Dataview’ query. Expression.Error: The index cannot be negative.
Details:
Value=[List]
Index=-1

And it happens after this step 

= Table.NestedJoin(Custom1, {"PRODUCT NUMBER/ SKU"}, #"SKU Price bracket", {"Sku #"}, "SKU Price bracket", JoinKind.LeftOuter)

Dataview query is loading without any issues or errors. 

Can someone please help or let me know where I should look for solution. Thanks!

[v-cgao-msft]

Hi @Zoru ,

The error message suggests that a list is being accessed with an index of -1, which is invalid. Review any steps in your query that involve list indexing or operations that might result in a negative index.
Ensure that the columns specified in the function exist and contain the expected data. A mismatch or unexpected null values could potentially lead to issues.

Best Regards,
Gao
Community Support Team

If there is any post helps, then please consider Accept it as the solution  to help the other members find it more quickly.
If I misunderstand your needs or you still have problems on it, please feel free to let us know. Thanks a lot!

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[PawelWrona]

Please investigate both tables before joining. Error may appear on this step, but it doesn't mean that this is caused by this step.

JestedJoin reads all the data to perform the operation. Therefore, it will load all the rows, where you might have errors which don't appear in Previews (where you deal with limitted data). Try go to both tables from before join, and use Table.SelectRowsWithErrors function to find the step which is causing your error.

[lbendlin]

Do you have null values in the join column for the left table?