Pb with syncCto (and Composer)

Hi everyone,

Not sure where to post this as my problem is a bit complex.

I got a productional website under Contao 3.5.12 with Composer and SyncCto extensions.
I got the local dev version of this site on my Mac in Mamp environment.
I'm used to synchronise them with SyncCto.

As I need to make some modifications, I first want to synchronise from productional to local ("synchronise server" button).

In the local website
But there is the blue point in front of the client line which is to say "The extension CtoCommunication or syncCto is not installed". When trying to sync, I get the message : "Error on transmission, with message: 403 Forbidden".

In the productional site :
In the left column of the backend, Synchronization is installed.
In Package management, I don't see menatwork/synccto (nor contao-legacy/synccto).
But when I check "xx dependencies installed" both appear but there is a "no entry" symbol on the syncCto line http://lesnouvelleshybrides.com/syst...s/removing.png

What's wrong with Composer ? How to make synchronization work again ?
Thanks.