I was doing the quest to kill the Ice Wraith to join the Stormcloaks when I left my follower, Marcurio, on the side of a cliff because he was getting in the way.
After I completed the quest, I went back to find him, but I couldn't. So, I went back to Riften and found him at the Bee and Barb, where I recruited him. When I speak to him, he acts like I've got a follower and says, "looks like you've got someone already," and stuff like that.
How do I fix this so that he will follow me again?
If you are on PC, then type the following command into the console (which can be opened with the ~ key):
set playerfollowercount to 0
If you are on console, then all I can say to do is to load a save.
Try getting arrested, that works for me when one of my followers stopped following me.
Maybe load an old save? That should work. When something happens in a game that you want to undo, you can usually go back a few save files (provided you have one that goes to where you want), which will set your progress exactly as it was at the moment of that save file creation.
Note that you will lose all progress after that save file was created, so rewind time with caution.
