The Noah 4 upgrade should automatically migrate the license file from a 3.x license to a 4.x license. This can be verified by looking for the license file (noah4.lf) in the following folder:
C:\Program Files\Common Files\HIMSA Shared\Noah4.lf
C:\Program Files (x86)\Common Files\HIMSA Shared\Noah4.lf
Copy the license file (Noah4.lf) from a machine that currently has a Noah 4 license (see path above) or download it here.