The pitch went well, and the investor is interested. At the next stage, they’ll send their own technical expert to go through the code, servers, team, and documents. This process is called technical due diligence, and many deals slow down or lose value right here.
The cause is usually not catastrophic: undocumented code, dependence on a single developer, a server with no backups. But for an investor, each of these is a risk, and risk means a lower valuation.