A technical error in the build process of the latest FWsim updates has caused the application to crash on startup as of today. This problem affects versions 4.2.1.9, 4.2.1.10, 4.2.1.11, and 4.2.1.12.
A component used to protect the software was incorrectly configured with a technical expiration timer. This is why the software worked correctly for the past two weeks but stopped functioning today when that timer was reached.
Because the application cannot open, the automatic update feature is blocked. You must manually download and run the fixed installer to restore functionality:
Installing this version will replace the broken program files. Your show files, custom effects, and settings are completely safe — they will not be affected by this re-installation.
I sincerely apologize for the disruption to your workflow. We have already taken steps to ensure this does not happen again.
Lukas Trötzmüller — Founder, FWsim
February 3, 2026