Please confirm the platform you're using, Adobe Express. Is it the mobile app (Android/iOS or the desktop web app? Could you please share a screen recording of the entire workflow using the Gen AI brush and its failure to work as required, so that we can understand and investigate the issue?
If you're using a web browser, have you tried working in private/incognito browsing mode or on a different recommended browser, such as Safari, Firefox, Chrome, or Edge?
Please share your observations along with the device make and model details (browser details if applicable) so we can assist you.