Issue:

RingCentral is forcing users that are outside of the organization to create an account before joining the RingCentral meeting.

Fix:

Disable "Only Authenticated Users can Join" setting in RingCentral.

1. Click Settings in the bottom left of RingCentral.

2. Click the Video tab.

3. Find Personal meeting and click Edit 

4. Click Advanced settings 

5. Turn off Only authenticated users can join