I made a few D-class amps fullbridge it didn't work

I see two IR2110 drivers , buffer transistors and a bunch of high speed MosFets, plus sizeable output inductors, looks very much Class D to me .

But we do nothing with a mystery PCB alone, post the whole project, schematic, construction notes, pictures, etc.
 
It´s impossible to answer with no data, not even a schematic.

Classic Class AB amps can bre managed with minimal data because they are mature technologies, with decades of experience behind,.

Mounting, layout, power supply, can be safely left in DIYer hands, as long as he has *some* experience.

On the contrary, Class D amps are new evolving Technology, actual building instructions must be detailed, specially because high/RF frequencies are involved, layout is CRITICAL.

And power supplies are typically SMPS so a full can of worms on their own.

A beginner should think twice before embarking in a complex and incomplete project.

4KW bridged Class D amp?
Poorly/no documented?

I wouldn´t recommend it even to a enemy.