If you can make calls from Hangouts, there's nothing wrong with your account, at least theoretically.

Perhaps you've denied Voice the use of your microphone or you have some sort of "security" software running that's blocking it from working correctly. Try opening voice.google.com in a private tab in Chrome (you'll have to log back in, etc) and see what happens. And, obviously, if you're running some outdated or oddball browser, try using a real browser like Chrome, Edge or Firefox.