Had to re-install new movie studio 17 platinum suite because it would not open after 1 day...now it says that the serial # is not valid or it is already used.. whats going on?

System is an Aspire TC 1780..Intel Core i5 13400 processor..16 GB memory..512 GB ram... Intel uhd 730 graphics.. windows 11

Now I cannot uninstall this programme,,it says that it is still running..cannot see where its running and how to close it..can you help?

Thanks