Share with other Nextcloud

hi all,
i have two nexcoud server update all at last stable vesion.
all is up and running well!
only one think is not clear to me…
i want to share a folder between to user of different nexcloud server:
from the server A i share a folder to USER@SERVERNECLOUDB.com but the user of the b server don’t see anything!
what i have mistaked?
thanks all and good day!

please review the docs might be this helps:

https://docs.nextcloud.com/server/stable/admin_manual/configuration_files/federated_cloud_sharing_configuration.html

Also see

thank you so much for your help!!!