The upload button has disappeared. How can I fix this?

I’m using the esp-web-tools library to upload firmware. It used to work, but I’ve noticed the install button has disappeared. How can I resolve this?

Here’s my code:

    <esp-web-install-button id="installButton" manifest="assets/flash//manifest.json"></esp-web-install-button>

Code :

website :
https://monkhumcc.github.io/mon2-flash-tool/