Problem while inserting float

I am using LyX Version 2.3.4.2 (Friday, February 7, 2020), pdfTeX 3.14159265-2.6-1.40.20 (TeX Live 2019/Debian) in Ubuntu 20.04.1 LTS.

I was using Lyx and it was running fine for quite few weeks.

Suddenly, I got this error. While inserting a float, Figure caption is showing UNDEFINED. In pdf output, Figure is not coming. I am attaching screenshots.

%% LyX 2.3.4.2 created this file.  For more info, see http://www.lyx.org/.
%% Do not edit unless you really know what you are doing.

documentclass[english]{article}
usepackage[latin9]{inputenc}
usepackage{graphicx}
usepackage{babel}
begin{document}
This is an error I am facing.
begin{figure}
begin{centering}
includegraphics{wan}
parend{centering}

end{figure}

end{document}