SQL Permissions Error on setup (The SQL service account login and password is not valid)

I was installing several SQL instances for a SCCM pre-prod environment that was going to mimic a production build but on a much smaller basis.  I was using a specific AD account and it had to span 3 domains in the same forest.  In the first domain (where the account existed) I had no issues. Once I went to the other 2 domains I kept getting the same 2 errors, namely

"The SQL Server service account login or password is not valid"
Or
"The credentials you provided for the Reporting Service are invalid"

I make as many mistakes as the next so I wrote down the username and password on notepad and then opened power shell as that user (so I deffo knew I was using the correct username and password)

I am crap at reading past error messages but the second error caught my eye

So it is telling me here that if I have an issue with the domain account I can go and change that in SQL Configuration Manager.  So I can perform my install with the standard built-in accounts and then change it when the install is done.  But the really important thing here is that  you can't go to services.msc and change the account that any of the SQL services run under as this will not allow SQL to properly configure the services.  One of the things that the SQL configuration does is grant the user the right to logon as a service. (that might have been my issue but it still does not make sense when SQL configuration manager can make the changes)

When you jump onto SQL Configuration services and select the SQL services and change the user account from the built in account to the domain account you want.

Now you can see that I have all the services changed to domain accounts, except for the Reporting Service

 To change the SSRS you need to logon to the SSRS Configuration Manager, before we can change the account to a domain account we need to backup the encryption key.

Now when I look at the SSRS page there is a domain account and not a built in account

And the same can be seen on the SQL configuration manager page 

 There are 2 last points here, if you are installing SCCM you must use network accounts you cannot use the build in SQL accounts and if you are running these services under a domain account then you will need to register the SPN.