Does a buyer's financing struggle give me room to renegotiate a higher price?

Not directly, though it can shift the dynamics of the negotiation in your favour in other ways. A buyer's financing difficulty generally isn't a reason for you to demand a higher price for the same business, since the business's value to that buyer hasn't changed just because they're struggling to fund it. What it can do is give you leverage over deal terms and timing: whether you're willing to extend a financing condition deadline, consider a vendor take-back to help bridge their financing gap, or simply decide to keep talking to other buyers while this one continues working on funding.

The nuance is that a financing condition in a purchase agreement typically exists to protect the buyer, letting them walk away if they can't secure funding, so a buyer's financing trouble more often points toward the deal not closing at all rather than toward you extracting a higher price from the same deal.

If a buyer is struggling to finance the purchase, it's worth deciding, with a business lawyer, whether to help bridge that gap through structure, such as a vendor take-back, in exchange for terms that benefit you, or to treat it as a sign to keep other options open rather than assuming the price itself is now negotiable upward.