Hello, we're sorry you having issues.
First off, can you please double-check that all players can connect with each other in the party chat.
Then, can we make sure no user is using a wireless internet booster/extender or having their connection currently run off multiple routers.
Can we also confirm no user is using communal internet? For example, a University accommodation.
Once all of the above has been checked, can we ask all users to try connecting via ethernet/LAN cables.