Bug with Dropbox with Dropbox API 59

When i try authentifiate in Dropbox to create sandbox i get this error :

DropBox API: (59) Unknown cipher in list: ECDHE-xxxxxxxxxxx

i try to use this :
add_filter( ‘backwpup_cacert_bundle’, ‘__return_false’ );

but no effect

https://wordpress.org/plugins/backwpup/