If you purchased a license but are getting an error, try the following steps:
The most secure and reliable fix for any licensing issue is to maintain an active subscription or purchase an official license directly from VanDyke Software. securecrt 87 3 license key fix
If your key is too old for version 8.7.3, check the VanDyke upgrade page to see if you qualify for discounted upgrade pricing to the latest supported version. To help pinpoint your issue, let me know: If you purchased a license but are getting