Hello,
The device has by default enabled monitoring of login attempts, and, once the number is reached beyond a certain value, firewall rule is generated and access of the WebUI is blocked for the IP address, which has tied to connect.
However, if you only failed to enter password for the WebUI, access over SSH should still be possible. There you can edit /etc/config/ip_blocked file by deleting the entry of your blocked IP, then restart firewall with /etc/init.d/firewall restart command.
You should be able to access WebUI again afterwards.
Best regards,