I'm not sure why you find the sentence "weird". The action happened and it is complete, so the simple past is perfectly acceptable.
I just got out of a meeting with the city planning commission where I was given approval for my construction project.
In this case the approval is a single, discrete action. There is no need for the present perfect which often implies continuous or repeated actions that continue up to the present moment.
In the case of your example, it's a difference that makes little difference:
The group was upgraded. (Upgrading is a discrete action that is complete)
The group has been upgraded (Upgrading is an ongoing process that is now complete).
The use of "was" vs. "has been" simply reflects the opinion of the designer, whether that person thinks of the upgrade as a single, short event, or as a process that takes time.
Side note: The writers of an application should make sure all of this kind of messaging is consistent -- they shouldn't use "was" in some cases and "has been" in others. This consistency helps the end user feel the application is stable and reliable -- that it will always return consistent results.