When you move, you are required to report your new address to the registry office. In some areas the registry office will report your new address to the immigration office, in others you must do this yourself.
If you do not do this and they have noticed that you have left, they will assume you have left the country permanenty and invalidate the residence permit.
Since you don't mention where you moved to, what you must do next will depend on that circumstance.
If you have moved within Germany and reported that to the local registry office, then you must bring the received registry certificate to the immigration office and, belatedly, report your change of address.
If you did not report your new address to the registry office, then you must do so now. This may incur a fine.
If you have moved outside of Germany, then you are no longer a resident of Germany. It will not be considered a refusal of entry.