I often hear that founders will leave investors' discussions without concrete feedback that helps them understand a reason for a decline. There are four factors I see most often leading to a 'no' or 'not right now' response when a company is raising a growth round.
The business is early for a fund's investment criteria. Many growth funds invest above a certain ARR or revenue threshold, so will often say 'not right now' when they meet a company that is earlier than this and agree to stay in touch for a future round.
The business model is not a match with a fund's investment criteria. Many growth funds specialize in a single area e.g. technology, software, consumer goods. The network and experience that investors bring to each new company is specialized to this given area, so a business outside of this is a better fit with another similarly focused fund. You can learn this ahead of time by looking for similar companies in a fund's portfolio (usually listed on their website or a source like Crunchbase).
A company's financials are outside of the fund's investment criteria. Many funds look for businesses that meet their growth, capital efficiency and retention criteria. A miss on multiple of these criteria can lead to a 'no' but important to know that a miss on one is often not enough to kill a deal. I've seen companies with very high growth + little capital efficiency and very high profit + little growth be highly competitive.
Negative customer feedback. This is harder, but important. Sometimes everything will go right and initial market checks will reveal that customers are unhappy or likely to churn to competitor. An initial 'yes' may turn to a 'no'.
Factors 1, 2, and 3 are a matter of fit and represent a majority of the reasons I've seen firms pass on a investment opportunities. Tailoring your target list of investors through a fundraising process will ensure that you are spending the most time with those focused on your stage and type of business. Continuing discussions with the best fit firms that may have said 'not right now' earlier on can make your next round of funding quick and easy.