A common problem I have heard and a something I hear on a daily basis too. There's pretty much only one reason why your planted aquarium won't pearl. You're either not using CO2 or not using anywhere enough.
A healthy aquarium that is running CO2 will show lots of O2 bubbles. The below clip shows a super healthy tank once the CO2 has been turned off - that's right. No CO2 is running at all and look at all the O2 bubbles. The aquascaper has done this by injecting enough CO2 so that his drop checker turns that wonderful green colour. When it hits that green, you know you have 30ppm CO2 in your tank and guess what? Your plants begin to pearl (release O2). You're then treated to mother nature at her best.
If you're not getting pearling in your tank and you're using CO2, the question is, are you using a drop checker with bromo blue solution?