The session cannot currently be used for multiplayer...

Hello there, after going over problems on #trainz within the game, I ended up reinstalling the game and managed to get a few multiplayer sessions going on mojave. After I quit out for a while and come back, all of the mojave sessions give me this error when trying to start one:

The selected session cannot currently be used for multiplayer.
The session, the route, or some dependencies are not built-in and are not available on the Download Station.

I know I have all of the dependent files because I've successfully used the sessions atleast once each and there doesn't appear to be an issue for connections because I can still run the default Debrecen session included with the vanilla install.

If anyone can help me figure out why the mojave sessions have stopped working after I've got them running successfully in the same install, please do so.

all the dependent files must be on the d/l station....

what's that supposed to mean? I've already established that the activity worked, past tence, and stopped working, giving that message instead. I would also like to add that I've reinstalled the game again and it works though I have a feeling the solution is temporary

You have to upload the MP Session to the DLS.