If you have a number of installed copies biger than a number of purchased licenses then your serial number may be blocked on server. But there are a lot of situations when you have to reinstall the plug-ins many times on new computers and etc. So, if you have met a situation what your serial number is blocked then it is not a critical problem. You can try to unblock the serial number self with follow online form. If it is possible then you'll be able to register more copies of the plug-in.
2021.07.14 - the LaunchBox util lets to launch old IntelMac plug-ins into M1 Photoshop. See details
2021.07.12 - Apple's Silicon M1 processor and native Photoshop2022 support now! See details
2021.06.12 - Oscar award for special effect with using our plug-ins! See details
2021.04.01 - Now all out Photoshop plug-ins are adapted to MacOS11.2 BugSur