As far as I know, you don’t need to be logged into Twitter to see the ads. You will automatically see all ads, irrespective of geography, language or targeting using the tool.
The simple explanation is ether a) no ads on the accounts or b) since it was launched only a couple of days back, it’s still glitchy, and will be fixed soon.
Twitter has been promising this transparency center from October 2017, then kept postponing the launch every month until they gave us a hard date of “25 June 2018”, and finally releasing on 29 June. So I would not be surprised at all if it’s super buggy.