Before trying another flowering fertiliser on bougainvillea, observe the balcony where it actually grows. Buildings, roof overhangs and nearby plants can leave a bright-looking space with relatively little direct light.
Check the position at several times of day. Note when the plant is shaded and whether that pattern changed since it was bought or moved.
Separate light from the potting problem
Inspect the root ball, drainage and watering routine too. A plant in a suitable bright position can still struggle in a container that remains wet, while a well-drained pot cannot supply missing sunlight.
Record recent pruning and feeding. Repeatedly cutting back every extension while adding more feed makes it difficult to understand the plant's response.
Confirm the variety and local growing season before expecting a particular display. Make a suitable correction and watch subsequent growth. Do not use severe drying as a shortcut to force flowers from a plant whose condition you have not assessed. The first task is to understand the site and the root environment, not to make the plant experience a succession of new stresses.
The RHS bougainvillea guide places actively growing container plants in full sun and explains that flowers develop on current-season growth. Those details make actual exposure and recent pruning relevant to a poor display, alongside the condition of the roots.
Related reading: Bougainvillea Not Blooming? Light, Pots and Pruning.