Other things you could try doing:
1. Restart your TRB and try then.
2. Go to "Network -> Firewall -> General settings" menu and enable "Masquarade" & "MSS Clamping" checkboxes in LAN > WAN zone. Try then.
3. Lastly, check if your connected device doesn't have any additional firewall that could stop you from reaching it.
EB.