fix(rdb): reviews 2

Author: ldecarvalho-doc

pages/managed-databases-for-postgresql-and-mysql/troubleshooting/database-instance-connectivity-issues.mdx

@@ -47,6 +47,7 @@ I cannot connect to my Database Instance through a Private Network.
 
 ### Possible causes
 
+- The Database Instance TLS certificate is outdated
 - Client network issue
 - You have reached the maximum number of connections
 - The Database Instance is experiencing instabilities due to a high load