Hi Oliver and welcome to Advanced Instaleler forums,
This may happens if you are running the .MSI and not the .EXE. Please note that the "Azure" theme that you are using requires "Enhanced User Interface" which is handled by our EXE Bootstrapper.
In order to enable the "Enhanced User Interface", you can go in the "Themes -> Settings tab" and select "Always (install, uninstall and maintenance)" option.
Also, when you choose a theme that requires Enhanced User Interface from the "Themes" page, the package type is automatically turned to EXE in the "Media" page. Then, when the project is built it creates an EXE setup file and the MSI file next to it (the MSI file can also be included in the EXE file). When you run your package, you should run the EXE file for the bootstrapper to handle correctly all the dialogs and controls.
This is happening because Windows Installer is not able to manage our
Enhanced User Interface.
Can you please see if the behavior still persist after running the .EXE and make sure that the Enhanced User Interface is enabled? If it does, can you please attach the ico file so we can further test and investigate this?
Best regards,
Dan