Komatsu D31 16

I am new to this forum and this is my first post. I have a Komatsu D31 16 Dozer. I had the hydraulic lift cylinders rebuilt. Fluid level shows full but no response. Is there a way to bleed the system? The cylinder has a 1/4" plug and I removed it but still no response. There is no fluid coming through the lines. Any ideas what to do? Thanks Jim

Komatsu D31 16