Before more people make the same comment about "not being able to play MP on a payware route": That was not his question / comment.
Installing the route blocks playing (some) MP sessions on routes that worked before installing it. Reason: It has 1 or more items that are an update on items on the DLS which have not being made available via the DLS. Since MP requires all items to be 100% the same (so not older or newer) it results in making it impossible to play those sessions.
My advice to the OP is:
Delete all dependencies that came with the Maria Pass X route install and then download those (missing) dependencies again from the DLS. That should solve your problem.
If you happen to find out which asset(s) are the conflicting assets, be sure to tell us so others know which specific items to look for / avoid.
I hope this makes it all clear. If not, please let me know which part is still fuzzy.