In the case's env_run.xml file:
If CONTINUE is set to false, change it to true and then submit.
If CONTINUE is already true, then just submit.
This way, the simulation should continue from the most recent restart files that were written in the case's /run directory. The model does this by reading the rpointer files found in the case's /run directory.
This will not work if the model cannot find restart and rpointer files in the /run directory. In that case, you will need to start the simulation over and avoid exceeding the runtime limit by running a shorter simulation.