I understand that you're facing challenges in plotting the received signal from a Pluto SDR using the Time Scope block in Simulink.
You should ensure that the sample rates on both the transmitter and receiver sides are compatible and correctly configured. Mismatched sample rates can lead to unexpected behaviour. Also, configure your blocks to have a reasonable number of samples per frame. Very large frames can lead to high memory usage and system instability.
Instead of using the "TIME SCOPE" block for continuous streaming signals, consider using blocks like "Spectrum Analyzer" to visualize the frequency domain and try to limit the duration of data displayed in the visualization tools. Plotting a very long signal can lead to high memory usage.
For further information, refer to the documentation link below: