Rstudio fails to be displayed on my laptop (client) when trying to X11 forwarding from my Imac (server) at home

I am trying to display Rstudio on my laptop (where I have Ubuntu 18.04.5 LTS) using X11 forwarding with ssh to connect to my Imac at home. I set up all the files (ssh_config and sshd_config) on my Imac (which I am using as a server) to allow the forwarding. I also install xauth on my Imac. However, when I connect to my Imac using ssh -X username@IPAddress and launch Rstudio with open -a Rstudio, Rstudio opens on my Imac but its not displayed on my laptop. However, if I launch xterm, a window opens up on my laptop, making me think that the connection I set up is correct. I also tried to reverse the process, which means I tried to ssh into my laptop (in this case used as server) using my Imac and launch firefox, in this case the firefox window is displayed correctly on my Imac. What am I missing when I try to display Rstudio on my laptop? Thank you for your help. Riccardo