Hi I have wired up my battery the wrong way around and now have no power getting to my main fuse under the seat . I have tested and recharged the battery changed the main fuse and nothing . I used a meter tested the battery it was good then tested the main fuse red + side and get nothing I thought that the main fuse went straight to the battery but now I'm guessing not any ideas would be great cheers

[2015 Z Force 800 53/Trail EPS]

There has been a number of actual fuse holders go bad because of some bad internal crimps. Maybe you had one that was close but went over the edge when it was hooked-up backwards. Probe the main wire just before the fuse. If you have power, probe it just after. If no power then you have your answer.
Wouldn't hurt to double check all other connections and grounds as well. The main battery usually grounds to the engine but the chassis ground is a smaller wire from it to the engine. It may have burned.