Cannot save target file with a .xlsm file

I started working on a .xlsm Excel file. When I tried to export it, Studio said the worksheet name was longer than 31 characters. I then altered the Project Settings to not translate the worksheet name. Still no luck. Then I tried to recreate the project, reimporting the original .xlsm file into Studio, only to have Studio 2017 tell me that this file type is not supported. So know I can still open the first project I created, but I cannot export it, and can't seem to create a new project or open any other .xlsm files on Studio. How can I fix this?