Saved Passwords not syncronising between devices?

So I just switched OS on my desktop, and had to log into Firefox all over again for the first time in a bit, and it turns out that for some reason my saved passwords arent synchronising with my whats saved on my phone? In the past my experience have been that if I ask firefox to save my password on one device it remembers it on all my devices. Is this not the case? Is there something I need to do to manually synchronise?