Website spits out PR_CONNECT_RESET_ERROR in firefox's incognito

So I have a site that uses letsencrypt and ssl works fine when I'm browsing my site in firefox. The moment I try browsing my site using incognito mode in firefox my browser throws this secure connection failed error and spits out PR_CONNECT_RESET_ERROR.

I can't seem to come to a solution and it only happens in firefox. Chrome & Edge works in both normal & incognito windows.

How exactly do I fix a PR_CONNECT_RESET_ERROR ?

I had the same problem and the solution was for me to enable the ssl_session_cache

I'm using nginx so I had to add the following line in my config:

   ssl_session_cache shared:SSL:10m;