I have to presume that your loan officer is acting in an ethical manner and is not asking the seller or their agent to engage in any acts of fraud, etc. So, if everything is on the up and up, I'd have to say....
Geez. How childish and unhelpful can you get? Most agents want to move the deal along and will cooperate with all parties as long as the actions are ethical and legal, BUT, they can choose not to, soooooooo...........then I have to ask why the listing agent needs to deal with your loan officer at all?
You are dealing with your loan officer. Your agent, the selling agent would be the person to deal with the listing agent, not the loan officer.
The agents have an obligation to take your offer to the seller. If the seller accepts an offer with a mortgage contingency, the seller has an obligation to allow an appraiser onto the premises. If the seller accepts an offer with contingencies for inspections, the seller has an obligation to allow inspectors onto the premises.
Frankly, I see no obligation for the seller or their listing agent to deal with your loan officer.
Who knows. Maybe the listing agent has personal reasons for not helping but I think you can move the transaction along with the help of your selling agent alone.