CRM is complicated. Very.
If not-for-profit organisations were just selling widgets, CRM would be simple. But they're not - most organisations have 10s of income streams with all sorts of different ways of getting paid. On top of that, a lot of them even have pretend money called soft-credits (how we pay our team).
Setting all that up in one system that wasn't ever designed for the purpose might work...but then it might not. And you can be sure the CRM vendor will tell you it was someone else's fault it didn't work.