When creating a licence for a location and adding an Office to this agreement, you may see that the dropdown for offices does not contain any values.
To troubleshoot this please check the following on your products (space>products)
Check that the office has been 'made available' at the chosen location
Check that the record type is an office
Check that the start date of the office is not in the future and that the end date has not passed.
Check that the product record is not Discontinued.
For more information on creating offices in Operate, please see this article