Unable to 'save' or 'save as' after importing and editing musicXML file

I'm a newby here, recently transitioned from Finale. I saved all my Finale files as XMLs and recently started on my first MuseScore project which is an orchestration which beautifully imported as a musicxml into the software. But the problem is that it won't let me save it (and I'm afraid to close it as I've made changes already). The initial command-S gave me a window with the option to save online or on my computer. Every time I chose to save on the computer, it didn't bring me to any window to do so. I clicked the box not to show me that window again just to work past it using the File menu. But similarly, under the 'File' dropdown menu, the only options which are bold are 'New', 'Open', and 'Import PDF'. No option to click on 'save' or 'save as'. And the shortcut shift-command-S also does not work. (I am using Version: 4.4.3.242570931 and fairly new MacBook Pro, Ventura 13.6.3.) As an experiment, I created a New file and started a new arrangement just to see if it would save as Muse file. It did. So the problem seems to only be in regards to my .musicxml file. Please help. File attached for anyone who wants to jump in.