I think Saras Sarasvathy's Effectuation Model offers some excellent guidelines on how to approach building trust and developing a viable business relationship. See https://www.skmurphy.com/blog/2010/02/07/saras-sarasvathys-e... and https://www.amazon.com/Effectual-Entrepreneurship-Stuart-Rea... for more on this.
Jerry Weissman's "Understand-Believe-Act" sales model is also a very good fault tree to use in diagnosing where your efforts may be stalled:
Understand: do prospects understand what it is you can do for them (here vision generation and simple explainer demos can help as well as basic case studies with clear examples).
Believe do prospects believe that you can deliver the results you promise (here technical proof demonstrations, benchmarks, case studies, references can all help).
Act: Do they have a reason to act. Are you addressing a critical business issue or a nice to have. What is the total cost of implementing your product (not just your price but any changes in workflow or practice or infrastructure that will be required). How does this compare to value. Is there a critical event or date that offers a strong reason to act.
See https://www.skmurphy.com/blog/2007/08/08/understand-believe-... and https://www.amazon.com/Presenting-Win-Telling-Your-Story/dp/... for more on Weissman's model.
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