Fix grammar in cause description

Author: aartig13

support/dynamics-365/customer-service/omnichannel-for-customer-service/active-conversation-form-not-showing-as-configured.md

@@ -21,7 +21,7 @@ You might encounter the following issues in the **Active Conversation** form:
 
 ## Cause
 
-The issue could be caused due to the **Customize Active Conversation form** setting is disabled.
+The issue could be caused by the **Customize Active Conversation form** setting being disabled.
 
 ## Resolution