RIR4 Max and MATLAB communicate via a feature called the Matlab Filter.
This is possible because MATLAB is registered on your system as an automation server. This sets up the MATLAB engine so that external applications such as RIR4 Max know which version of MATLAB to talk to.This registration may disappear, for many reasons. When this happens, MATLAB is still present in the list of RIR4 Max filters; it is still possible to select an .m file. It apparently tries to loads but its execution fails.The solution is to manually re-register the server.
Method 1: Register from system prompt
To register MATLAB as an automation server from the Windows system prompt, first open a Windows Command Prompt using the Run as administrator option, if necessary.
Move to the folder containing the executable file for the MATLAB version you want. Then type "matlab -regserver," and press Enter.
MATLAB will now display a minimized command window. Open this window and exit MATLAB.
Method 2: Register from the MATLAB Command Prompt
Run MATLAB as an administrator. Then, in the Command Prompt window, type "regmatlabserver," and press Enter.