SCCM - Waiting for content, and Software Centre Cannot Load, how do I trace the problem?

Hello,

Running SCCM Current branch version 1606.  Deployed a new child primary without any issues, and can distribute content to that primary without any issues.

I have also been able to without issues deploy the client from the child primary to clients.

Now I need to deploy packages and applications using the child primary.  Multiple errors:

> When I deploy one application to multiple clients the first error I see is that on the software catalogue on the clients it just says waiting to download and stays at 0%
> On some clients the application is downloaded/installed successfully but when I try to deploy software updates it fails to receive them

All other clients on other sites are fine, so it is something specific with this child primary.  I've checked/tried the following to resolve it:

>  Changed the distribution settings for the application to "Automatically download content when packages are assigned to distribution points" - This stopped the clients from trying to download the application completely and it just says "past due".  When I then try to manually click install it brings up an error message stating that Software Center can not be loaded (attached)
>  Checked the BITS and .net are installed correctly on the Primary
>  Restarted the clients and the primary
>  Checked the boundary setup is correct and that there is not a duplicate.  It is and I don't think i would be able to deploy the client if this was incorrect
>  Reinstalled the SCCM client on the client machines

I'm also not sure which log files I should be checked for error messages, either on the primary, or the cas, or the client itself, as different clients seem to get further than others.

Grateful for any help

Thanks
Screen-Shot-2017-09-22-at-12.26.15.png