This question has been answered by clutchmarketing. See the first response.
It sounds like a JavaScript issue -- possibly a conflict. Try checking with Chrome Dev. Tools (Ctrl-shift-i) and see if it reports any JS errors.Thanks BobRay. I did that and it said there was indeed a JavaScript issue. I looked up the error message "TypeError s[i].search is not a function in modx.tree.js" which I then found a post for in the MODX https://forums.modx.com/thread/89234/manager-javascript-error-typeerror-s-i-search-is-not-a-function-in-modx-tree-js