VirtualBox - Windows 10 Host + Linux Mint 19 Guest - All ports (8989, 9091, etc) work on guest, but NOT on Lan

EDIT: Solution Found. In my case, I needed to go into the network settings, in the identity tab change the Firewall Zone to "trusted". My setup: Host: Windows 10 Virtualbox: Version 6.1.36 Guest: Linux Mint 19 Tara Network: Bridged mode, IP 192.168.0.x Various services (Transmission, etc) are accessible within the guest. I.E., I can navigate to their web pages locally. Transmission, for example, can be accessed within the guest via 192.168.0.x:9091. However, it and all other services are NOT accessible outside the guest, on the Lan. * Guest Firewall (ufw) is disabled for testing purposes, issue remains. * Guest VPN (private internet access) is disabled for testing purposes, issue remains. * I can ping the guest, and the guest can ping out to devices on the Lan. * Guest can browse the internet. * Guest SSH is operational. * (edited to add) - bypassed windows firewall by trying to access on android phone, same issues It's a real head-scratcher. Everything was working fine and then it just stopped working. As it happens, I have a backup of this VM, and when I spin up the backup instance, THAT works perfectly. For about three days, and then everything stops working again. So this issue is absolutely reproducible, but I have zero knowledge of how to track something like this down. It seems all the TCP/IP stuff is in order, and it seems the apps should all work fine. But something is preventing them from being accessible outside the guest/on the Lan. Any help would be highly appreciative. Please tell me what log files you might need/how to retrieve them. Thank you.