I have seen a corrupted Photoshop preferences file cause issue when getting to the save step before. Please reset the Photoshop preferences. Then restart Photoshop and try again. In the preferences, under the General section, select Reset Preferences on Quit. Then restart Photoshop.
I’m not sure if that will fix it. However, we need to test it first because I have seen this fix it before. If it doesn’t fix it then we can proceed with the next troubleshooting steps. Let me know after you have done this.