License Server response has not passed data integrity check: Invalid signature format
Attempt to obtain license from the server leads to the error
License Server response has not passed data integrity check: Invalid signature format. The issue is caused by an outdated version of Floating License Server used to obtain the ticket.
Starting with the 2018.2.1 release of JetBrains IDEs (released in Q3 2018), products no longer obtain license tickets from the old versions of FLS (versions prior to build #16429 which was released on March 19, 2018). To find the version number of FLS you are using, look in FLS log or in the web interface.
Update FLS to the latest version by following the upgrade procedure.