1) The failure to write/find the 'minmax' files is a venial sin, in that it doesn't actually affect any important part of 3dttest++ or 3dClustSim's usage further on.

2) However, the failure to read the .sdat files -- as you see -- is catastrophic, as those are the temporary files that store the results from the permutation/randomization. Did your screen output contain some progress reports after the line

   ================ Starting ClustSim calculations ================

There should be a lot of output following that about the jobs it runs to produce the .sdat files, before it then runs the 3dClustSim program. Are there any error messages there? You can increase the verbosity of the progress reports by adding option "-verb" to the 3dttest++ command line.

Offhand, it seems to me like perhaps there was some disk I/O issue -- I have seen that before, when using a scratch SSD space (for speed over network or rotating storage) that got full.