"Save as" command and convert to pdf are not working

I have just installed LibreOffice on my new MacBook Pro. I’ve been using this program for years, most recently, on my old MacBook Pro. I moved files I’d created with the older version to the new computer with the newer LibreOffice software but when I try to “Save as” or convert to a pdf, it won’t work. I get a long spinning cursor and then nothing happens at all. Can anyone help me solve this? I frequently need to use these! I always save my files as Microsoft .docx or .xlsx and all the files I moved are already saved this way.

It is a security feature by Apple to prevent ransomware attacks. You need to give LibreOffice Full Disc Access. See this 3rd party site Explained: What is Full Disk Access & Full Permissions on macOS Mojave