Accelerator simulation mode cannot rebuild and run simulation

The situation:

We are trying to do a BER test on our modulator. Doing so requires us to send on the order of 10^5 or 10^6 input symbols. This is a very long simulation time. I have been looking into integrating multithreading into the testbench by wrapping the DUT inside a “For Each” block. According to online documentation, doing so (together with other steps that maybe you can help clarify) should result in better parallelizing the jobs to improve runtime.

The problem:

I’ve modified the files that you’ve given me to replicate the problem (see attached). When I try to compile the block diagram (CTRL+D) I get this error message:

The parameter 'Simulation mode' of the Model block 'cpfskmod_003_tb/Subsystem_to_parallelize/Model' is set to 'Normal'. However, the Model block is inside subsystem 'cpfskmod_003_tb/Subsystem_to_parallelize', which contains a For Each block ('cpfskmod_003_tb/Subsystem_to_parallelize/For Each'). Simulink currently does not support this scenario. Consider changing the parameter 'Simulation mode' of 'cpfskmod_003_tb/Subsystem_to_parallelize/Model' to 'Accelerator'.

So then I go and change the cpfskmod_003 to “Accelerator” and attempt to compile the block diagram again. It takes some time to churn through some simulation build process I’m not too familiar with. And then spits out another error:

Unable to find model reference simulation target '\\etbc12i.ast.lmco.com\ctmp\n5220g\ngi_radio\modulator_nco_block\model\cpfskmod_003_msf.mexw64' for model 'cpfskmod_003', which is referenced by Model block 'cpfskmod_003_tb/Subsystem_to_parallelize/Model'. This could be because the top model has 'Rebuild' set to 'Never'. Change the 'Rebuild' setting and try again.

I then click on the ‘Rebuild’ link and change the setting to ‘Always’, which I would think would get rid of this problem. It does not, and I get the exact same error message.

Do you have any clues about what might be going on under the hood as to what’s happening here? I’ve seen the same issue pop up in other contexts when I’m trying to compile existing testbenches / Simulink models other people have written as well.