HTTP Error 503: Service Unavailable on New Install


Brand new install of Server 2016 and Aras Innovator 12 (latest service pack).

I've installed IIS with the default options, as well as under development > ASP 4.5, 3.5 and plain old ASP. 

Have Installed Visual C++ 2015 x86/x64, ASP Core for Web hosting and all other pre-requisites. 

Still get the error when browsing to the website. 

AppPools stop for Innovator Server and Default App Pool. Error in event log was due to being unable to read config file so have given IIS_IUSRS Read access to the innovator virtual directories and inetpub.

I've followed everything I've found online to no success! Anyone able to help, please?

Currently tearing my hair out!

Thanks in advance!