Mine show foliage only for at least a month before any sign of a bloom stalk. I've never timed it since all is well if there is foliage. The size of the claw will determine how many blooms are produced.

I would dig up one that hasn't sprouted to see if it is still viable or rotting.

The best way I've found to avoid rot is filling the planting hole with straight sand and pushing the claw into that. These guys demand drainage and I have ammended clay soil. Their beauty is worth the extra work. Unfotunately gophers love them.

Ranunculus will do nothing in a spring planting. Their bloom cycle is dictated by day-length (they are short day flowerers) and they really need to be forced into growth in January and given 3 months of increasing daylight to bloom well. As soon as the vernal equinox goes over, it is largely game over. If you do decide to persist with these tricky plants, autumn is the best time to plant, keep[ing them dry and fairly dormant and watering after Xmas which will start them into growth. Consequently, many of them do better under glass or with some protection so they can make sufficient foliage to bloom before daylength dictates that their season is over.
You have done nothing wrong - nurseries persist in selling these little tubers at the worst time for growing success.

I would just add that growing ranunculus successfully anywhere outside of coastal SoCal in the US is going to be a real challenge. Unless you can start in a greenhouse :-)) They just have rather specific growing requirements that are not easily met with inground planting across most of the country.

Here is an excerpt from a previous thread on this topic that presents the situation very well:

Ranunculus are a cool season plant with a frost sensitive rhizome. In
an ideal climate (like Carlsbad, CA) you would plant the rhizome in
late fall and it would put out roots and then leaves from December -
February and then bloom in March or April. After that it would go
completely dormant during the hot dry summer. The problem with trying to
grow them in the ground in cold climates is that the rhizome is not
cold hardy so you can't plant it in the fall and let it get established
in preparation for spring blooming. If you have have nice cool summers
you can probably plant it in early spring and have a summer blooming
season but then you will have to dig it up and store it in a frost free
location over the winter. If you have hot summers (like me) it doesn't
work to plant it in the spring because the plant doesn't have enough
time to get established before the weather gets hot and triggers the
blooming process. Without being properly established it will put only
small weak blooms or none at all. I've tried several times and had only
limited success growing it in the ground. I do have a nice one that is
about to bloom in a pot and that may be an option for you if you have a
cool sunny location for the plant to grow along during the winter.

This link of the Carlsbad CA flower fields - where virtually all of the ranunculus for the cut flower trade as well spring potted nursery stock comes from. A very impressive sight but this is an area that is uniquely suited to these rather tricky bulbs.