Hi, I just install bo3 mod tools and when I launch it and want to create a new map he says, "could not find map template" but I have the template folder on "rex\templates". I don't know why he does that. If someone can help, he's welcome.

Are you creating the map correctly? When you put a template like, the zm template you need to put zm_ before your map name, if you were making this and getting this error, try to verify the files integrity,if this don't help, well, remember, this mod tools is buged as fuck 
Steam support for files integrity: https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335
Hope it helps