There are three main reasons you might be unable to move a product seat between two licenses under the same Master License.
Different License Options:
Master licenses support a mix of license types, i.e. it is possible to have an Individual license and a Designated Computer license under the same master license. However, product seats can only be moved between licenses that are the same type.
Products can only be moved between licenses if all activations on both licenses have current validation status. If any activation on either license has overdue validation, you will not be able to complete the transfer.
What is validation and how does validation work?
Not current on Maintenance:
A product can only be moved between licenses if it is currently up-to-date with their Software Maintenance Service.
Learn more about MathWorks Software Maintenance Service:
If you need assistance with transferring products between Licenses in the same Master License, please contact MathWorks Support.