inout line undefined

I can see the process (referred to in the error) working properly in the simulation. All is well until in_EN goes low. Meaning the proper waveform is shown on the proper lines. When in_EN goes low the simulation just does not go further, I can increase simulation run time but simulation it self does not go any further.

If I start the program with in_EN low, the simulation runs for 15ns only and the io_SD line is shown undefined. And same thing occurs, I can increase or decrease simulation time but it does nothing when I increase it past 15ns.