Just to clarify for everyone facing the same issue: To fix the problem, in C4D go to your logo path layer > object tab > make sure 'Close Spline' is checked.
When I was making this tutorial at the time I mentioned "The use of the backdrop is to provide additional ambient lighting that is reflected on the edges of the logo's surface. Whilst not necessary, I believe it improves the overall appearance of the final render. That's to say, you are free to do it without a backdrop, but it may give you a totally different result - this is just my technique" but @envy in the comments below said that you can uncheck the camera visibility of your background object via cinema 4d properties > render .. > camera visibility so it keeps the reflection of the light on your text on... Just use whatever works for you! :)
what was the point of adding the studio canvas thing? you could've just rendered the model with no background, making it transparent, completely eliminating the need to mask it out afterwards.
The use of the backdrop is to provide additional ambient lighting that is reflected on the edges of the logo's surface. Whilst not necessary, I believe it improves the overall appearance of the final render. That's to say, you are free to do it without a backdrop, but it may give you a totally different result - this is just my technique :)
