iOS14 calls immediately go to voicemail

Here are some possibilities:

• Go to the Phone app, Recents. If a phone call that you should have received is not listed the call isn't getting from your carrier to the phone. Contact your carrier.
• The Mute switch on the left side of the phone. It should be towards the screen (no red showing if you look at it)
• Do not Disturb - If there is a crescent moon in the top bar on the Control Center go to Settings/Do Not Disturb and turn it off
• Volume - with the Home screen displayed press the Volume Up button (on the left, just below the Mute switch) and watch the volume setting on the screen.
• Settings/Phone - Silence Unknown Callers - if this is on calls from numbers not in your contacts will go to voicemail
• Settings/Sounds & Haptics - Make sure there is a sound assigned to Ringtone

Just a stab in the dark:

Mac: Connect your phone, open a finder window, select your phone. Select the “music” tab, select “genres” and check that box.

Windows: ??? Is this still done through iTunes?

iPhone 8, iOS 14, whatever the latest version of Mac is...

There have been so many rude and unthankful responders tonight. I won't offer any assistance here either. And I thought your omniscience was always on! In another thread someone other than the OP told a Community Specialist to not bother providing a response if they don't know the right answer.

I have absolutely no clue what the post above has to do with calls going to VM?

Go to Settings > Do Not Disturb Is it turned on? If yes, turn it off.

Absolutely useless information...

We tried all of that!

I am SO sorry that my mind reading skills are not up to your standards. I won’t even try to respond to you in the future, as you clearly expect people who respond to you to be omniscient.