"I'm sorry..." is not an adequate response to someone expressing that they don't feel prioritized.
The only appropriate and applicable responses are confirmation that said person is not a priority or showing said person they are a priority.
I rearranged a whole weekend just to kick it with a homie I haven't seen in a few months..and previously a few years.
No matter what's going on he will always reach out to see how I'm doing and always reminds me that I have a standing invite.