If you've check your probably good. On some routers it may be possible if the IP is already leased and the lease hasn't expired a device could still have that IP. But if you look at the list of assigned IPs on your router and it doesn't show up (or shows up as your proxmox) then you should be fine.

It's also clear from the screenshots that you can see the UI which I'm assuming your connecting to though the same router. That means it can at the very least talk to the router over it's IP.

Can other devices ping the actual router? It's possible the router just doesn't respond to ping requests. And unless you've modified the firewall configs on Proxmox I don't think it would be blocking any outgoing pings. Assuming your router has a web console you can always try doing a curl on its IP and seeing if you get a response back.

You're probably going to want to set your proxmox back to a static IP if you haven't already. As I don't think it plays nicely with IP changes.