Installazione photoshop versione prova su imac sierra

Hi I have an iMac sierra with internal hd failure, so for the moment I'm using an external hd. That said I can not install the trial version of Photoshop, since it gives me error 22 (the installation in case-sensitive volumes is not supported ,,, select a different volume). I then tried to install on other external hd but always the same error, I also formatted a new hd with different alternatives but it was a failure, what other alternatives do I have?