this window is displayed because of a conflict with your Cinema 4D license. This usually means that the license is being used more than once on the same network, which is a breach of the MAXON End User License Agreement (EULA).
MAXON permits Cinema 4D users who have a valid MAXON Service Agreement (MSA) to install their license on a second device (for example, on a desktop and a laptop). However, the simultaneous use of both installations is not permitted.
If you forgot to quit the instance running on a second device, please do so now.
If you require additional Cinema 4D licenses, we offer attractive pricing for the purchase of additional licenses*.
Contact MAXON or your nearest reseller for details.