While working from home, when dialing a phone number for an outgoing call on my desktop app, once i click on the green phone, nothing happens. I used to be able to make calls from home; this issue started about 3 weeks ago - any ideas?

When working from home, I type in a outgoing number from desk top app, when I click on the green phone icon, it doesn't begin ringing. It had been previously working, just began having issues about 3 weeks ago. Any idea what is causing this and how to fix?