We're having difficulty identifying the plants as the foliage looks more like that of Clivia than Agapanthus (which usually goes by the name Lily-of-the-Nile or sometimes African Lily). Both plants are native to southern Africa, so their common names could be confused. Do you have any tags or labels from the original purchase that show which species this bulb was supposed to be? Since the two plants require different care, the distinguishing between them is important.

Does this container have drainage holes in its base, and are they able to drain freely (as in, not blocked)? Is the soil being allowed to dry for an inch or more in depth before the pot is watered? Has it been fertilized at all this summer? If the plant has been stressed by over- or under-watering, it may have experienced some root damage, which could stunt the top growth. Lack of nutrients can also stunt growth if the potting mix has been depleted.

A full sun exposure would be fine for Agapanthus, but is probably too strong for Clivia, which normally has darker foliage. (Lighter green leaves on a normally dark-leaved plant can indicate too much light.) Agapanthus blooms in summer and will tolerate winter temperatures down to approximately 10 degrees. (In the ground; in a pot, they are more susceptible to cold damage. Even in the ground, our average minimum winter temperatures are lower and Agapanthus is not considered to be reliably winter-hardy here.) Clivia has greater cold sensitivity and should be brought indoors when autumn night temperatures reach about 50 degrees. They then need a chilling period (not as cold as for the Agapanthus) in order to flower in late winter or early spring. Here's more information for growing Clivia:

https://marylandgrows.umd.edu/2020/01/29/qa-why-is-my-clivia-plant-starting-to-yellow/

https://www.extension.iastate.edu/news/yard-and-garden-brighten-winter-clivia-plant

Miri

Upon doing some research, it seems that there are different types of Agapanthus, some which go dormant/die back in the winter while others go through a winter rest with green leaves. We are not aware of either type being winter hardy outdoors unless you have a very protected micro-climate outdoors.

We notice in your photo that the lower right corner suggests more information is on the reverse of the label. Take a look and see what it says.

In any event, these plants (and Clivia too, fyi) can take several years to settle in and begin to bloom. They are more likely to bloom well when potbound. 

We wouldn't fertilize now, as they will enter a rest period shortly, and should be taken indoors before frost, situated in the brightest light you can give it, and barely watered during the winter.

More information can be found at this page from the Missouri Botanical Garden: 

http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a433

Christine