The error message may appear after 1st Rider startup (just after activating 30-day evaluation) and may look like this:
Rider stores a couple of settings related to evaluation license in its configuration files. If these config files are corrupted for some reason, evaluation check is not passed, resulting in this error.
- On Windows: delete "C:\Users\<USERNAME>\.Rider2017.1" folder from disk.
- On Mac OS: delete "~/Library/Preferences/Rider2017.1" folder from disk.
- On Linux: delete "~/.Rider2017.1" folder from disk.