EX2100 doesn't show or connect to ONE specific Mac

Like the title says. I’m writing this from our Mini that cannot see the EX2100 on the network. I’ve created Alias-es for some folders on the NAS and it prompts me to log in my username. Except it won’t accept the CORRECT password. While my Macbook right next to me can see it under the Network tab AND login easily on command with same credentials.

Made sure that only one login is live at time to not mess it up.

Any help? I’m using the NAS as a bridge for certain files - like a home dropbox…but it ■■■■■ if it keeps doing this.