Libre Writer is saving documents in (.UOT) File

I did open LibreWriter and I did write a letter.I clicked save as : and gave it a name.I tried to open the letter but did not open. LibreWriter did save the documents in (.UOT) FILE.It should save the documents in ODT file.I did open Associate a file type or protocol with a specific program ,clicked UOT,clicked change program,chose LibreWriter,and clicked close.
The file is not changing and it is open by : Uniform office format text document.
In the beginning,when I did start having problem the UOT FILE was associate with LibreWriter and the Writer could not open the file. I cannot change the association and when I go to Property I change to Librewriter but is not working.This is the first time in around 10 years that I have this problem.
Thank you
OS: Windows 8.1,Librewriter

LibreOffice version? Which OS?

LibreOffice (64) Microsoft Windows 8.1