Zoom, mostly the issue is answering from the mobile app. It may not answer an incoming call or send an outgoing call. This is also an issue from desk phones too. Common issue are as follows: 

Dear Zoom Support Team,

I am encountering an issue with my Zoom OAuth integration. I am using an admin-managed account, but I cannot find the required scope for calendar access. When I switch to a user-managed account, I receive the following error:
{
    code: 4711,
    message: invalid access token, does not contain scopes: user read user admin, user read user
}
If I do not specify any scope, the token API (https://zoom.us/oauth/token) provides me with a token. However, when I use this token to call the calendar API, it gives me the following error:
Access Token Missing Required Scope: calendar read list calendar list

Please provide support to resolve this issue. 

When calls are made through the Zoom Phone/Hubspot integration and if their number is not associated with a contact, the call will not show in the Hubspot call log (activities).

This behaves differently from Hubspots own phone system (where they show up as 'unknown') and would skew any inbound call volume statistic reports in hubspot.

I have been working through the process and documentation to upgrade our Zoom for Salesforce plugin to the newer Zoom for Lightning plugin. I've been through the various steps to install it into our Salesforce org from the AppExchange, and then working through the Zoom documentation to customize it. When I get to the instructions for Setting up user access for the Zoom for Salesforce Lightning app, I look in Salesforce Setup at Manage Connected Apps, but Zoom does not show up there.

So when my users try to log in to the Zoom call center within Salesforce, from the Utility Bar, they see a message: "Warning: The current product is not active." 

I tried opening a ticket with Zoom Support, but they just sent me here to the Forums. I'm hoping someone has an idea of what I might be missing. Thank you.

Hi everyone,

Is SMS to short codes not supported by Zoom Phone? We have rolled Zoom Phone for about 5 months now and I've observed that our users can receive SMS from short codes just fine but they can not reply. If anyone attempts to reply or send a new SMS to short code they get an error. 10DLC works just fine both in and out for SMS and our users love it but for some reason we can not SEND SMS to short codes; just receive?

For example, Samsung 74863 or any other 5-digit long legit U.S. short code.

Thanks

Boyan

Please for details review this post - reddit.com/r/Zoom/comments/1gqbu1n/where_in_the_phone_app_i_can_manage_audio/

I use google pixel phone.

Where in the phone app I can manage audio settings - chose headphones? Only for zoom sound does not go to headphones, all other apps work perfectly

Context - My phone has Bluetooth on, and headphones are connected to it. Any other app I used automatically uses for audio these headphones, including other calling apps.

Zoom - I join a zoom call - by default headphones are not used for audio, sound just goes loud, when I click on the button you highlighted on screen shot, the sound goes silent and to listen in I need to put my phone to the ear, as when I speak on the phone. bluetooth device, in this case headphones are still not used.

Reinstalling app was already tried, did not solve it.

And I just no way can find such a crucial setting and impact is huge, I am not able to participate in criticall calls/meetings, so feeling very desparate