For the first one, the ride is on another world (not one of the two offered for that day). The ride was listed on the screen that appears after pairing (located on the upper right hand corner), but i could not actually click on the join button.
For the second one, the ride is located on the same world. The program even took me to the starting corral, but it took forever to locate the group, and I had to bail, as the group wasn't located.
Among other quibbles, how do I do late join after I start riding? I cannot use the companion app to do this because the event disappears from the companion app after the start time has passed, regardless of whether there's a late join option.