1) You're a Start Up.
Most banks want to see a business fully up, running, and reportable. If you are not all three three, prepare to look elsewhere.
2) You don't have hard collateral to pledge.
Banks will typically attach all available hard assets, i.e. real estate holdings, both commercial and residential.
3) You want an SBA loan.
Surprisingly enough, many banks and credit unions do not participate in the SBA loan program. In terms of certain aspects of commercial financing (LTV, Equity Injection, Credit, etc), there is really nothing comparable to an SBA loan.
4) You want to buy a franchise.
Many local banks and credit unions do not have the procedural infrastructure set up to underwrite and properly manage a franchise loan.
5) Your credit union is approaching their lending cap.
Federally chartered credit unions are limited in how much they can lend in relation to the loan volume currently on their books.
6) You own a cash based business.
If you own a cash based business, like a restaurant, bar, salon, or bodega just to name a few, and you have difficulty in terms of traditional loan documentation, banks are simply not an option.
7) You're caught up in your bank's portfolio re-balance.
Banks like to achieve a certain harmony in their loan servicing portfolio. Having too much of one product (Investor loans, for example) and not enough of another (Deposits) is not desired and can result in your loan either being shelved indefinitely or denied altogether.
8) Your credit score is on the low side.
Anything less than an "excellent" score of 700+ will require not only some explaining and documentation, but will often lead to a denial or a reduction in the amount you are ultimately approved for.
9) You or your business is no longer wanted.
This one sounds harsh, but in reality, at the end of the day, banks and credit unions must be able to properly service your loan and manage their portfolio. If your business is underperforming or you are not as communicative with your financial reporting as you should be, both are grounds for the bank to exercise their call option.
10) Your business wants to expand to another state.
Most community banks and local credit unions will only lend in their state (or even county) footprints. If you are looking to expand out of state or move your business, you'll need to explore other options.