Your request for info or help does not contain enough info for anyone to be certain of the proper advice to share..
What version of Trains are you trying to run this on? Note that JR is offering two versions of Eagle River. The lastest version requires at least 19sp5. The older version can run on TANEsp4 for certain and perhaps an earlier version.
Have you used Content Manager to check for your missing sessions? What does CM report about them? Missing dependencies? Faulty dependencies?
You can also see if the dome car is listed in CM as a train vehicle and if it has missing or faulty dependencies.
I tried to run the lastest ER version on 19sp1 and several assets were reported as faulty. At least one dependency had a build number of 5.0 which requires 19sp5 to run. But I don't really know if your situation matches what occured to me.
