After using the command /up 4 its not upgrading just states what tier it is instead.

Same here, seems the new update broke it

You are not alone. 

how to i fix the Error? i can do /up 3. only down work?

I have to reload the plugin before I can /up

I've had to do this too, but it doesn't last long until you have to do it again

Problem is a change in EnhancedHammer.cs is overriding BuildingGrades so like said above it needs to be reloaded every time the server is restarted.  Pain in the butt so hopefully the writer of BuildingGrades can fix it.

EnhancedHammer has replaced the 'up' chat command previously registered by BuildingGrades 
EnhancedHammer has replaced the 'grade' chat command previously registered by BGrade  
Loaded plugin Enhanced Hammer v2.0.6 by Iv Misticos 

when is the dev going to fix this?

i dont use enhanced hammer and have the same issue as above