Did the program install ok and activate? Are you able to open the program? Did you also move your data files to the new computer? Both the .tax2020 and .tax2021 files? You only need the tax return data file ending in .tax2020 to transfer into 2021.
After you get the program installed the first thing to do before you open your tax return is to update the program and install any state programs you had. Then open your file. So you first might need to start a fake return to be able to download the state program (go to FILE - NEW). Enter some basic information, then go to the state tab and download the state program. Then try to open your existing return, go to FILE - OPEN