Hi @mcmarchesi! Welcome!
I'm afraid you'll need to supply some more info in order for helpers to be able to understand your problem. Most error messages are difficult to understand on their own without seeing all of the code that they depend on (not just the one line that threw the error). It's almost impossible to sort out data import problems without seeing both the code that imports the data and some sample data that causes the same errors when imported.
Can you try making a self-contained reproducible example that demonstrates your problem? This should be complete, runnable code with all the necessary library() calls and some sample data that causes the same errors (this can be a subset of your full data set, for instance). For more specific info on how to do that, see the link! 
You might also want to take a look at this: FAQ: Tips for writing R-related questions