Wrong error message (A connection could not be made to the data source)

I'm using Power BI Desktop to update a semantic model from 2021. I need to update the name of the database server. After doing...

Transform data

Data source settings

select the data source

click Change Source...

correct the value in Server

OK

Close

Apply changes

...I get this error message.

Cannot load model: We couldn't connect to your DirectQuery data source or internal model. Double-check that your server and database names are correct, and that you have permission to access them.

ProviderMessage: <ccon>A connection could not be made to the data source with the Name of '{"protocol":"tds","address":{"server":"oldservername","database":"databasename"},"authentication":null,"query":null}'.</ccon>

I have manually checked...

Transform data | Data source settings

File | Options and settings | Data source settings

...and the M for all 34 tables in the model to verify that "oldservername" exists nowhere in the .pbix file.

What's happening here? Where else to I need to change the server name?

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I'm leaving this here for anyone who has this problem in the future.

It turns out a column had been removed from a table. I was also seeing this error message.

Expression.Error: The column 'ColumnName' of the table wasn't found.

Details:

ColumnName

Removing the column name from the semantic model caused Power BI to stop lying to me about not being able to connect to a server name that it wasn't even using.

All is well.