I've been following this addon since it was on chrome and even considered switching, but finally the firefox version appeared late during 2017. Unfortunately i have the same issue as the previous reviewer, the subscription manager section loads infinitely. I included a video here. https://youtu.be/a2omrEc_I_o

My main browser is cyberfox 52 but i checked on various firefox versions. I never got it to work on multiple versions from 52 to 56 but it works on 57. Sadly i can't use firefox 57 due to many plugins i use for school and work not being available with the new system. However, this addon claims to work on firefox 45 and up.

One thing i noticed while writing this post is that all versions i tried are 64-bit, maybe it's a 64 bit bug? i'll be trying when i can a 32 bit install but in the meantime this is the bug the other user mentioned.

In short: Doesn't work on firefox prior to 57 despite claiming to work on 45 (all 64 bit versions).

Edit: Thanks for your quick answer. Saw you promptly changed the version requirements. I hope i can try it out eventually.