problems with web app

I have been tryng to use the online voice recorder from https://123apps.com/ on my iPad Air 3. When I open it with Safari, it says it does not work with that browser so use Firefox or Chrome instead. I then tried it with both of those, but they tell me there's no microphone. I need to use this particular app for an online class. Can anyone help? I've tried to find settings to give the browsers permission to use the microphone, but have had no success. There's no problem with my microphone when I use Zoom or Voice Memo or Easy Voice Recorder.

I've used the app successfully on my desktop PC - when I open it there, I get a request to allow the app to use my mike. That request never appears on the iPad.