It is a common question in Forums why Uninstall button is disabled in Software Centre :
There are quite interesting things needs to know the reason behind it :
1) If the software is deployed as "required" , it is not possible to uninstall from Software Centre. However the user can go to Programs and Features to uninstall it. But the software come back as installed after the next Application Deployment Evaluation Cycle if it is not able to detect it.
2) If the software is deployed as "Available" then the uninstall button will be shown in software centre once the application is installed successfully. This button is used to uninstall the application without requiring administrative permissions for the available deployment based application. There is a known issue that if the MSI application doesn't have a uninstall cmdline then uninstall button is not valid but currently it is enabled.
3) If the software is created using Package/Program then it mayn't be valid.