server was not found at //Server:7046/DynamicsNAV90/Service

Now lets check for if your service is running or not from services window

that is in RUN window type services.msc and click OK 

You can your service running if not right click and start the service.

now check again ...RTC

for running service you can also use the Administration Tool for 2013 and 2015 , 2016 NAV versions