Sorry for being slow on this (caught me travelling)... while there
is an ISOLDE version on the Toolshed for ChimeraX 1.5, I'd definitely recommend updating to 1.7 for a host of reasons. That being said, it's not clear to me why the installation should be hanging, but the most likely culprit is some issue causing the download to time out. One thing you can try is to use your normal web browser to go to
https://cxtoolshed.rbvi.ucsf.edu/apps/chimeraxclipper and
https://cxtoolshed.rbvi.ucsf.edu/apps/chimeraxisolde and download the Clipper and ISOLDE packages for your OS and ChimeraX version (if you have a reason why you
have to stick with ChimeraX 1.5, you'll need to click on the Release History tab and scroll down until you find Clipper 0.19.0 and ISOLDE 1.5). Then in ChimeraX, on the command line type:
toolshed install
... then drag-and-drop the ChimeraX_Clipper...whl file from your downloads folder onto the command line and hit return to install it. Do the same for the ChimeraX_ISOLDE...whl file, restart ChimeraX, and you should be ready to go.
Best,
Tristan