Connection works between primary to secondary but if I swap then no longer working

I use Multiplicity on a work laptop to share KM on my personal desktop, so I can control both with one set.

Primary is on my work one, secondary as personal. If I try to swap roles, I can't connect from personal to working one.

I already tried to set the firewall as private, create rules, and so on, but nothing works.

The work one uses a VPN, but even if I disconnect it, it doesn't work. On the personal one, I have Kaspersky, and on the other MS Defender.

Do you know what can be the issue?