Hi @Seb,
To mitigate unwanted calls, all phone companies (including RingCentral) may proactively block calls connected to suspicious calling patterns. That is whay we don’t have a control over this. See https://www.fcc.gov/call-blocking.
Here's a recommendation to prevent this issue.
Since these are your long-time clients, you may add them as Trusted Numbers. This is a feature where you can enter a phone number from which you always want to receive calls.
How to enable:
- Go to https://support.ringcentral.com/article-v2/7251.html?brand=RC_US&product=RingEX&language=en_US&pills-nav=admin_portal
- Follow the instructions for managing blocked calls as an admin in the Admin Portal, number 7, letter B.