Getting 404 not found message on my site

For some reason today when I go into my site I get 404 page not found message on any category/product etc I click on, only thing working is homepage ? same on mobile device
www.3dlasercraft.com/store

Discovered problem I went back to last things I changed and I had enable seo urls, the htaccess is .htaccess so I dont know why it is causing a problem seems to be one thing after another with this opencart

Here is a good tut that may be of help

Thanks good link