Sort by Column missing a column option

I have a Power BI file that is pulling in data from Sql Server through a custom sql query. I have a column [Office] that is a combination of integer and text and is a text column- ex: "22 - Mankato". I have extracted the integer at the beginning into a separate column [OfficeSort], through the sql query, and have formatted it as a whole number. I wish to sort the [Office] column by the [Office Sort] column. For some reason I can't figure out, that particular column is not showing as an option in the Sort by Column list of columns.

Has anyone run into this? I can't seem to find an example through the forum/google of this particular issue. As far as I can tell, it doesn't have to do with the data formats of each column, as other whole number columns seem to be available in the list to sort [Office] by.

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