Hi Everyone,
I have built my own rstudio server on Ubuntu 18.04 and nginx is the webserver for it. If you are trying to upload files more than 1.5mb you will need to adjust the file upload size in the nginx.conf file. I have been fighting with this for over a year now with not a lot of ideas on SO or anywhere else.
I followed the guide below and was able to successfully upload files of up to 20mb. There may be additional configurations needed to upload even larger file sizes.
http {
...
client_max_body_size 100M;
}