License checkout failed - License Manager Error -4

When I open session on Matlab, it does not give error. While I am working, it gives error "License checkout failed. License manager error -4. Maximum number of users for Signal_Toolbox reached" and it dismiss me. I couldnot save my analysis. what is the reason for this error and what can I do?

Answer 1

[nl2605]

http://www.mathworks.de/matlabcentral/answers/101313-why-do-i-receive-the-error-license-manager-error-4