Due to updates with the spatstat package, the CRAN version of ENMTools is currently not working for some people. We've got a develop version on github that seems to be doing okay, though, so you can install that by typing:
install.packages("devtools")
devtools::install_github("danlwarren/ENMTools", ref = "develop")
We should have the CRAN version working soon. Sorry for the inconvenience; apparently all of the authors of packages depending on spatstat were supposed to receive emails months ago saying that all of this was coming down the pipe, but none of us seem to have gotten one.