I found a solution. This solution can help, I'll post it here.
- In your actuall Gnome personnal home folder go to .config/goa-1.0
goa = Gnome Online Account
1.0 at this time maybe it will be another version for you.
In goa-1.0 you should find a conf file « accounts.conf » If you have added an online account in Gnome parameters. accounts.conf example :
[Account account_1875320154_0]
Provider=owncloud
Identity=username
[email protected]
CalendarEnabled=false
ContactsEnabled=false
FilesEnabled=true
Uri=https://account-url.com
AcceptSslErrors=false
save and past « accounts.conf » in your new Gnome installation. Same folder /home/user/.config/goa-1.0.
A network link appears automatically in Nautilus
Go to Gnome paramaters --> @ Online accouts a warning message prompts you to enter your online account password. Enter your password and everything should be OK.
In my case, the post-installation script will create the accounts.conf file automatically.
It may not be the best way, but it works.
Et voilà :)