Bit n Bit help please

i just started to try using 2 bit carving and I need a little help. I uploaded a file it had a roughing code and finish code embedded. At the end of the roughing code the machine paused. I stopped the router and went to change bits. I could not move the z slider in order for me to access the bit. Any advice on what I need to do for a successful bit change.

Separate each tool into its own file.