Shame on you!

The human response to losing an account is to stay away because you think that the people you were once doing business with don’t like you anymore.

Foolish you. In all probability, the reason they stopped doing business with you is because you stopped paying attention to them.

Regardless of your “reasons” why not go back to former business associates, and find out what the current status is. I want you to go back as soon as you can.

No, that is not clear enough. I want you to contact all past clients within the next 7 days.
Now that is an objective for you.

What will you say to them?

Say you are sorry that it has taken so long to contact them again. Tell them that for whatever reason they decided to move on without you, you plan to address their concerns and provide them with a superior service. Apologize if necessary.
And then ask them for another opportunity to work with them.

Tell me this: What have you got to lose? They will remain yesterday’s news unless you do something about it.