can't connect to Proton Drive

[reborn13]

I'm using Linux Mint and currently trying FFS (free version) and it looks like just the application I'm looking for. It works perfectly for syncing folders with my external hard drive.
But I just can not not connect it to Proton drive. I click on the cloud icon on the top right in the FFS window, then in the next window that pops up I enter the server name (drive.proton.me) or IP address (185 70 42 40), followed by my Proton username and password all as prompted. I checked and re-checked all that but all I ever get are the following error messages:

Cannot find the following folders:
sftp://[my user name]@drive.proton.me
Cannot read file attributes of "sftp://[my user name]@drive.proton.me".
Cannot determine final path for "sftp://[my user name]@drive.proton.me/~"

Where could there possibly be a mistake? I'm totally stuck and would appreciate any help and advice. Thanks!

[xCSxXenon]

Proton doesn't support sftp from my search

[reborn13]

It doesn't support ftp either. Plus the google drive option in ffs is greyed out and when I hover over it, it says 'disabled' and refers me to a Readme document in the ffs folder. Which tells me that google drive seems to have a problem with Debian. Oh well, I'll soldier on.
Thanks! At least I know it's not some idiotic mistake of mine.