Apple computer users sometimes use Parallels to emulate running a PC so they can run NinjaTrader. One of the problems with using Parallels is that when it updates, it can change some of the emulated hardware on the emulated machine, so much so that it causes NinjaTrader's Machine ID to change. NinjaTrader derives your machine ID using a combination of information pulled from your computer's hardware and base configuration. Normally, device drivers, physical devices, BIOS, etc., do not change frequently on a PC, so these types of Machine ID changes happen rarely on PCs. But some users have their Parallels updated frequently and need to contact their indicator provider's support to update their license to match their new machine ID when it changes.
The following NinjaTrader support article refers to this issue, and the one recommendation offered by a former Parallels user is to switch to VMWare to avoid the problem. We can't speak for the merits of switching to VMWare for this reason, but it may be an option if frequent Parallels updates causes license issues with your 3rd Party indicators.