I am assuming you are trying to achieve a scenario similar to this, i.e., install a service and start it automatically.
Assuming you have made sure that you are really running as Administrator, i.e., the Admin command prompt or Run As Administrator.
Also, assuming you have restarted the machine to make sure that old version of your service is really removed, as you have tried multiple times to install / uninstall your service.
The error Access is denied
essentially means that the user running it does not have access. Since you have said that you are running as Administrator, it is possibly that even Administrator does not have access to start the service. May be you are in a locked down environment (likely via Group Policy), where only the Domain Administrator is the "most powerful" !
The next step would be to investigate the permissions your service has. A useful tool for this is: SubInAcl
https://ss64.com/nt/subinacl.html
Display or modify Access Control Entries (ACEs) for file and folder Permissions, Ownership and Domain.
SubInAcl /service "your service name"
The above command is not easy to use ! You need to download it from the Microsoft web site.
Another useful tool is the SC
command. This would normally be available by default.
Service Control - Create, Start, Stop, Query or Delete any Windows SERVICE.
SC sdshow "your service name"
would give details of the permission.
This would give you data which can help in further investigation.
You could also start / stop the service with this command. You can try with this to check whether you are getting the same exception when using this tool as well.
The following serverfault question gives some details about setting permission to a service
https://serverfault.com/questions/187302/how-do-i-grant-start-stop-restart-permissions-on-a-service-to-an-arbitrary-user
If you want to see the Stack trace from installutil
you can use the /ShowcallStack
option
https://learn.microsoft.com/en-us/dotnet/framework/tools/installutil-exe-installer-tool
/ShowCallStack
Outputs the call stack to the log file if an exception occurs at any point during installation.