In my experience, I have tried to SSH into my router (I guess too many times) which resulted in my web UI not loading for me any longer. So I set a static IP that wasn't currently assigned to anything and I was able to load back into the web UI. Before I switched IPs I was able to log in to the UI on my Proxmox VMs, which meant the UI was still reachable (if you can still ping the IP in CMD or Mac/Linux Terminal you should be good to follow the same instruction).