On Fri, 31 May 2019, Jürgen Spitzmüller wrote:
\usepackage[pdftex]{pdflscape}
Added to the preamble.
As said, your MWE outputs correct with pdflatex here (see attachment), so
I don't know how to help.
Viewing the attachement I see the last page still in portrait mode. That is,
the content is horizontal and cut off on the right side rather than rotated
90 degrees counter-clockwise with vertical text and everything visible.
An expanded MWE is attached.
Rich
#LyX 2.3 created this file. For more info see http://www.lyx.org/
\lyxformat 544
\begin_document
\begin_header
\save_transient_properties true
\origin unavailable
\textclass scrreprt
\begin_preamble
\date{}
\usepackage{gensymb,atbegshi}
\usepackage[pdftex]{pdflscape}
\usepackage{lipsum}
\@ifundefined{extrarowheight}{\usepackage{array}}{}
\setlength{\extrarowheight}{0.2in}
\renewcommand{\thetable}{\arabic{table}}
\end_preamble
\options abstract=on, enabledeprecatedfontcommands
\use_default_options true
\maintain_unincluded_children false
\language english
\language_package default
\inputencoding auto
\fontencoding global
\font_roman "palatino" "default"
\font_sans "cmss" "default"
\font_typewriter "cmtt" "default"
\font_math "auto" "auto"
\font_default_family default
\use_non_tex_fonts false
\font_sc false
\font_osf false
\font_sf_scale 100 100
\font_tt_scale 100 100
\use_microtype false
\use_dash_ligatures true
\graphics default
\default_output_format pdf2
\output_sync 0
\bibtex_command bibtex
\index_command default
\paperfontsize default
\spacing single
\use_hyperref false
\papersize letterpaper
\use_geometry true
\use_package amsmath 1
\use_package amssymb 1
\use_package cancel 1
\use_package esint 0
\use_package mathdots 1
\use_package mathtools 1
\use_package mhchem 1
\use_package stackrel 1
\use_package stmaryrd 1
\use_package undertilde 1
\cite_engine natbib
\cite_engine_type authoryear
\biblio_style plain
\use_bibtopic false
\use_indices false
\paperorientation portrait
\suppress_date true
\justification true
\use_refstyle 0
\use_minted 0
\index Index
\shortcut idx
\color #008000
\end_index
\paperwidth 6.5in
\paperheight 9.5in
\leftmargin 2cm
\topmargin 4cm
\bottommargin 2cm
\headsep 1.6cm
\secnumdepth 2
\tocdepth 2
\paragraph_separation indent
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\is_math_indent 0
\math_numbering_side default
\quotes_style english
\dynamic_quotes 0
\papercolumns 1
\papersides 2
\paperpagestyle headings
\tracking_changes false
\output_changes false
\html_math_output 0
\html_css_as_file 0
\html_be_strict false
\end_header
\begin_body
\begin_layout Section*
Introduction
\end_layout
\begin_layout Standard
This example is to get the pdflscape package working.
\end_layout
\begin_layout Standard
\begin_inset ERT
status open
\begin_layout Plain Layout
\backslash
lipsum{3-8}
\end_layout
\end_inset
\end_layout
\begin_layout Standard
\begin_inset ERT
status open
\begin_layout Plain Layout
\backslash
newpage
\end_layout
\begin_layout Plain Layout
\backslash
pagestyle{empty}
\end_layout
\begin_layout Plain Layout
\backslash
begin{landscape}
\end_layout
\end_inset
\end_layout
\begin_layout Standard
\align center
\begin_inset ERT
status open
\begin_layout Plain Layout
\backslash
bf
\backslash
LARGE{
\end_layout
\end_inset
Company:
\begin_inset ERT
status open
\begin_layout Plain Layout
\backslash
hrulefill
\end_layout
\end_inset
\begin_inset Newline newline
\end_inset
Daily Site Inspection Log
\begin_inset ERT
status open
\begin_layout Plain Layout
}
\end_layout
\end_inset
\end_layout
\begin_layout Standard
Blah, blah, blah.
\end_layout
\begin_layout Standard
\begin_inset Tabular
<lyxtabular version="3" rows="13" columns="3">
<features tabularvalignment="middle" tabularwidth="10in">
<column alignment="center" valignment="top" width="1.75in">
<column alignment="center" valignment="top" width="2in">
<column alignment="center" valignment="top" width="5in">
<row>
<cell alignment="center" valignment="top" topline="true" bottomline="true"
usebox="none">
\begin_inset Text
\begin_layout Plain Layout
\begin_inset ERT
status open
\begin_layout Plain Layout
\backslash
bf
\backslash
Large{
\end_layout
\end_inset
Date
\begin_inset ERT
status open
\begin_layout Plain Layout
}
\end_layout
\end_inset
\end_layout
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true"
leftline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
\begin_inset ERT
status open
\begin_layout Plain Layout
\backslash
bf
\backslash
Large{
\end_layout
\end_inset
Inspector
\begin_inset ERT
status open
\begin_layout Plain Layout
}
\end_layout
\end_inset
\end_layout
\end_inset
</cell>
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\begin_inset ERT
status open
\begin_layout Plain Layout
\backslash
bf
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Large{
\end_layout
\end_inset
Comment
\begin_inset ERT
status open
\begin_layout Plain Layout
}
\end_layout
\end_inset
\end_layout
\end_inset
</cell>
</row>
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<cell alignment="center" valignment="top" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
\end_layout
\end_inset
</cell>
<cell alignment="center" valignment="top" leftline="true" usebox="none">
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\begin_layout Plain Layout
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<cell alignment="center" valignment="top" leftline="true" usebox="none">
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\begin_layout Plain Layout
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</row>
</lyxtabular>
\end_inset
\end_layout
\begin_layout Standard
\begin_inset ERT
status open
\begin_layout Plain Layout
\backslash
end{landscape}
\end_layout
\end_inset
\end_layout
\end_body
\end_document
