you need to check both systems for firewalls and possible antivirus programs for blockages as well as your router and yes even some modems will have an internal firewall that you may need to configure
see https://support.ubi.com/en-GB/FAQ/9/...0000000ej6YCAQ
as well as
https://support.ubi.com/en-US/FAQ/9/...0000000eio0CAA
If you continue to have issues PLEASE open a support ticket with Ubisoft Support at https://support.ubi.com by clicking on My Questions in the upper left corner of that page.
You can also call them on the phone during regular support hours <--(BEST OPTION)
You can find phone number information here: https://support.ubi.com/en-US/FAQ/60...0000000eiChCAI
You can also try to contact them via social media.
Facebook: https://www.facebook.com/UbisoftSupport
Twitter: https://twitter.com/ubisoftsupport