@JuiceeSweet, is this issue occurring with just one landline phone? First, check to ensure the number isn’t on your Blocked List. If that doesn’t resolve it, there could be another underlying issue, similar to what's described in the KB article linked below.
https://support.ringcentral.com/article-v2/7550.html?brand=RC_US&product=RingEX&language=en_US