S.K.
I am not an expert, but I think the plants have to be pollinated by bees to produce any/good fruit. Maybe the netting is keeping the bees from doing their job.
Here is an excerpt I found online, it seems even if the strawberry flowers have both a stamen and pistils, it still needs help distributing the pollen.
"Flowers without stamens were common in earlier cultivars, and no fruit setting resulted unless pollen was brought from staminate flowers (Darrow 1927, 1937). Continued breeding and selecting has resulted in the hermaphrodite flowers in all commercial cultivars. However, hermaphrodite flowers may not be completely self-fertilizing. The stamens are so placed that when they crack open they readily scatter pollen onto many, but not necessarily all, of the pistils. Pollination of all of the pistils of a flower is necessary for maximum berry size. If all pistils are fertilized, a perfectly shaped berry should develop. If few are fertilized, an irregularly shaped berry or "nubbin," sometimes only one- fifth the size of well-fertilized berries, will develop.
Allen and Gaede (1963) studied fruit-setting of 'Shasta' strawberries in the greenhouse and showed that plants caged and undisturbed by man, insects, or breezes set no fruit; those uncaged and undisturbed set 20 percent; those uncaged but receiving wind from a fan over them set 77 percent; whereas those that were caged, but brush pollinated daily, set 97 percent of the flowers. This finding indicated that the plants alone set few fruits, and wind has some effect, but insects may be more important than wind as pollinating agents. Couston (1966) also noted that malformation of berries was greater when adverse weather occurred at flowering time. He also obtained more number one berries from exposed plants than from plants caged to prevent insect visitation, indicating that insect pollination increased production."
