Hi @ragas! Welcome!
I'm a little confused by this — it is true that sentimentr is not an updated version of sentiment (they are totally separate packages), so what package are you talking about when you refer to "the updated package"? (or maybe you intended to say something else?)
Can you explain this in more detail? How do you know the installation was successful? What error messages (or other unexpected behavior) do you see when you try to run the lines above?
Note: I believe you are interested in making sentiment — or something equivalent — work with R version 3.4.4., not RStudio (see: Differentiating R from RStudio) — RStudio still hasn't made it past version 1.2 
. I edited the post title accordingly.