Yes, that's the basic idea. The speaker is obviously being quite threatening here. My understanding is that the agency has already been engaged by the speaker's company, but the company is dissatisfied with the service received so far. The 'this' is the situation/relationship between the two parties, and the speaker is suggesting that the proposed discussion will help them 'make it work' ie find a way to make it successful.

I'm not a native speaker, but I think the expression means ''See if something can go right'' like Give something a chance to see if something can give positive results

"Make this work" is usually a positive expression that shows that a person wants to put in the extra effort during a hard situation to find a solution that everyone is happy with. It's a little bit strange in this context, but the speaker is saying that of the two choice he has, he would rather take some time to work on this business partnership before starting to look for a new agency to work with. People also use it in a very casual way when something doesn't go right, but they want someone else to feel okay about a mistake or something. For example, if a friend of mine tells me that she'll bring some food to a party, and then she forgets, she might feel bad because there's not enough food for everyone. So, I might say, "We'll make it work" to help her not feel so bad about her mistake.