topic Re: Failed to see data in the lakehouse in Dataflow

Failed to see data in the lakehouse

Emmanueldufour — Wed, 06 Aug 2025 13:20:03 GMT

Hello all,

I'm started to test Fabric and i'm currently facing some issues when synchronized data from my data flow gen2 to my new LakeHouse :

I'm using a gateway as i alway did when i need to connect the data but for some reason, i'm not able to refresh .

The strange thing is when i open the dataflow, i'm able to see the data:

Here below the error message :

There was a problem refreshing the dataflow: 'Couldn't refresh the entity because of an issue with the mashup document MashupException.Error: Error in creating lakehouse table in a version, InnerException: Tables can only contain uppercase or lowercase letters, numbers or the underscore character., Underlying error: Tables can only contain uppercase or lowercase letters, numbers or the underscore character. Details: Reason = Expression.Error;ErrorCode = Lakehouse036;Message = Tables can only contain uppercase or lowercase letters, numbers or the underscore character.;Message.Format = Tables can only contain uppercase or lowercase letters, numbers or the underscore character.;ErrorCode = Lakehouse019;Microsoft.Data.Mashup.Error.Context = User GatewayObjectId: e3fd85b1-6a7a-476f-937e-3aa575684f8b'. Error code: 104100. (Request ID: 87d839f2-c4a7-4ce9-ab3a-3c34a4058604).

Did you already encounter this type of issue lately ?

Thanks,

Emmanuel

Re: Failed to see data in the lakehouse

Anonymous — Thu, 07 Aug 2025 05:59:24 GMT

Hi Emmanueldufour ,

I’ve run into the same issue before and I can confirm it’s caused by invalid characters in either the table (query) name or the column names when writing from Dataflow Gen2 to a Lakehouse.
1.Sanitize all column names. In Power Query, add this step to ensure all column names contain only valid characters (letters, numbers, underscores).

Table.TransformColumnNames(Source, each Text.Replace(Text.Replace(_, " ", "_"), "-", "_"))

2.Rename the query/table name. Make sure your query name (on the left pane) is something simple like CustomerData no spaces, dashes, or special characters.
3.Remove extra rows and promote headers properly. If your preview shows rows like -1, -, etc., remove them using Remove Top Rows, and then apply Use First Row as Headers to ensure clean structure.

Once I applied these changes and clicked “Save & run”, the dataflow refreshed successfully and loaded into the Lakehouse as expected.

Hope this helps.

Regards,
Akhil.

Re: Failed to see data in the lakehouse

Emmanueldufour — Thu, 07 Aug 2025 09:26:05 GMT

Thanks Akhil,

It finally worked just like you suggested. I had to remove from all tables name the underscore.

Regards,

Emmanuel