Help with wither Farm

Hello people of EMC I have built a wither farm and once I had built it no withers where spawning I was looking if some one could help me with this because I would hate to tear it down so plz help

Pictures:

I can't really see good from the screenshots, but What block are they spawning on? They cannot spawn on glass, or top half slabs

.......well looks I hv some tearing down

You shouldn't have to tear it down, just replace the glass/slabs with full blocks

its a shifting floor design, but the area looks too large for a normal nether fortress, also your ticks might be too fast/slow

can some one come to the farm and see it better

What server, I may be able to check it out/give tips

smp7 and the farm is really laggy

Sorry, I can't go out on that server :/
If you would go further inside the machine , to where they actually spawn and take a few more screen shots, I could probably help a lot more

Here is the video of the wither farm https://www.youtube.com/watch?v=z_sHiBsV6rQ

I think i know why it won't spawn anything.

Withers and Blazes need to spawn on a nether brick block (Only the Full Block, half slabs will Not work) in EMC

That being said, Most, if not all shifting floor designs will not work for wither farms in EMC.

I have used this design with al my wither farms, and it works like a charm. I strongly recommend it
https://www.youtube.com/watch?v=tR6oATNOFSw