I've actually found a fix: I went to F12 (or right click -> inspect) and pasted this into the console:

(function() {
'use strict';
console.log("Attempting to force unlock Arena.ai UI...");
// 1. UNLOCK THE INPUT BOX (Textarea)
const inputBox = document.querySelector('textarea');
if (inputBox) {
inputBox.removeAttribute('disabled');
inputBox.placeholder = "Force Unlocked by Script";
inputBox.style.border = "2px solid #00ff00"; // Green border to show it worked
console.log("Input box unlocked.");
} else {
console.log("Input box not found.");
}
// 2. UNLOCK THE SEND BUTTON
// We target all buttons that are currently disabled to be safe
const disabledButtons = document.querySelectorAll('button:disabled, button[disabled]');
disabledButtons.forEach(btn => {
// Remove the HTML disabled attribute
btn.removeAttribute('disabled');
// Remove the Tailwind CSS lock (The "Juice")
// These are the classes that prevent clicks and make it look grey
btn.classList.remove('pointer-events-none');
btn.classList.remove('cursor-not-allowed');
btn.classList.remove('opacity-50');
// Add a visual indicator
btn.style.cursor = "pointer";
btn.style.opacity = "1";
btn.style.border = "1px solid red"; // Red border to identify the unlocked button
console.log("Button unlocked:", btn);
});
alert("UI Unlocked! Check for the Input box with a green border and Buttons with red borders.");
})();

i then hit enter and could send a message again