Meggy Jr RGB (like other soldering kits) will not work correctly unless every solder joint is solid. Certain joints are critical-- there are at least six different places on the board where a single solder joint being bad will cause the entire LED display to not work correctly. From what you've described, it's clear that there are incomplete solder joints, and there may be reason to suspect accidental bridging between other joints as well.

Please, go back, and *carefully* inspect the solder joints. Make sure that every one of them looks shiny, wet, and clear of debris and accidental connections, before turning on the Meggy Jr RGB.

I cleared all connections already. I just need to fill holes and what kind of debris?

The type of debris that can cause problem is little bits of conductive solder, left over from soldering.