The NIA rhesus monkey study found:

Calorie restriction (CR), a reduction of 10–40% in intake of a nutritious diet, is often reported as the most robust non-genetic mechanism to extend lifespan and healthspan. CR is frequently used as a tool to understand mechanisms behind ageing and age-associated diseases. In addition to and independently of increasing lifespan, CR has been reported to delay or prevent the occurrence of many chronic diseases in a variety of animals. Beneficial effects of CR on outcomes such as immune function, motor coordination and resistance to sarcopenia in rhesus monkeys have recently been reported. We report here that a CR regimen implemented in young and older age rhesus monkeys at the National Institute on Aging (NIA) has not improved survival outcomes. -- Impact of caloric restriction on health and survival in rhesus monkeys: the NIA study

The NIA study ran for 20 years on two groups of monkeys, "early onset" monkeys who started CR (or being in the control) at a young age and "late onset" who were older. As you'd expect, there were more age-related deaths in the "late onset" group (80 out of 90 monkeys) than the "early onset" (19 out of 90).

By contrast the WNPRC study found that CR did have a positive effect on lifespan:

Caloric restriction (CR) without malnutrition delays aging and extends lifespan in diverse species; however, its effect on resistance to illness and mortality in primates is not clearly established. We report findings of a 20-year longitudinal adult-onset CR study in rhesus monkeys aimed at filling this critical gap in aging research. In a population of rhesus macaques maintained at the Wisconsin National Primate Research Center, moderate CR lowered the incidence of aging-related deaths. At the time point reported 50% of control fed animals survived compared with 80% survival of CR animals. -- Caloric restriction delays disease onset and mortality in rhesus monkeys

The WNPRC study had 76 monkeys, 19 of which died from age-related causes.

There's a long discussion section at the end of the NIA article talking about differences between the two studies.