Answer:
There can be many reasons for this. Please send us the "authorization.txt" file, which you can create in RFEM/RSTAB using the program menu "Help → Authorization → Diagnostics". This is also possible in the demo version.
If you have changed your computer or formatted your hard drive without changing the partitions, please contact our hotline. You will then receive your existing license file with instructions for reactivating the softlock.