This is more likely to occur when Aldec Active HDL is trying to access a wrong or different license file.
The following are the suggestions:
1. Ensure that license.dat is placed at the following path : <Your Installation folder>\lscc\<diamond version>\license.
2. Check the environment variables and ensure that LM_LICENSE_FILE is pointing to the correct variable. If there are many paths, try placing the Diamond License path first, or try removing other license paths.