There are many reasons that flowers fail to emerge from their buds, and several effective ways to fix the problem.
Pruning Cannabis Plants — Why, How, and When
Cannabis Flower: A Beginner's Guide - The Heritage Club
Why Are My Buds Not Opening? How to Help Your Flowers Bloom
Should I cut yellow fan leaves of a cannabis plant as it finishes flowering? - Quora
Cannabis Flowering Stage How-to Guide
Pinching, Deadheading, and Cutting Back in Your Garden
Help! My Rosebuds Won't Open! Understanding Bud Ball on Roses
Why are my buds taking forever to mature?
How to Make Buds Bigger During Flowering
How to Grow Bigger Buds Outdoors - DripWorks
Here's Why Your Hydrangea Didn't Bloom
Why are My Rosebuds Dying Before They Bloom? – Black Gold
When to Harvest Cannabis & How to Know When It's Ready