R: package vignette not built - r

Question

Problem
I created a small internal package for my company. To describe hot to use it, I wrote a vignette. But for some reason, the vignette is not built when I hit Install and Restart in RStudio.
Further Information
I use roxygen for the package documentation
Interestingly, the output from Install and Restart says that it is installed:
==> devtools::document(roclets=c('rd', 'collate', 'namespace'))
Updating DataReportR documentation
Loading DataReportR
Documentation completed
==> Rcmd.exe INSTALL --no-multiarch --with-keep.source DataReportR
* installing to library 'C:/Program Files/R/library'
* installing *source* package 'DataReportR' ...
** R
** preparing package for lazy loading
** help
*** installing help indices
** building package indices
** installing vignettes
** testing if installed package can be loaded
* DONE (DataReportR)
devtools::build_vignettes() returns NULL even though the lines
Suggests: knitr, rmarkdown
VignetteBuilder: knitr
are included in the DESCRIPTION.
The YAML header of the vignette looks like this:
---
title: "My title"
output: rmarkdown::html_vignette
vignette: >
%\VignetteIndexEntry{Generate LaTeX tables for Data Reports}
%\VignetteEngine{rmarkdown::render}
%\usepackage[utf8]{inputenc}
---
I also tried to force building the vignette by devtools::build(vignettes = TRUE) but nothing changed.
EDIT (changed YAML header):
When I change %\VignetteEngine{rmarkdown::render} to %\VignetteEngine{knitr::rmarkdown} in the vignette's YAML header, devtools::build_vignettes() works and places the built vignette in /inst/doc/.
However, when I Check the package in RStudio, the check fails at this position:
** installing vignettes
** testing if installed package can be loaded
Error in namespaceExport(ns, exports) :
undefined exports: create_var_details, create_var_overview
Error: loading failed
Execution halted
ERROR: loading failed
Both create_var_details and create_var_overview are exported functions. Here an example:
...
#' #export
#'
create_var_details <- function(...
...
With the old header, the checks were fine.

Answer 1

I figured out that R did not find pandoc. Thus, I added the pandoc path to the PATH environment variable. I also changed the vignette enginge to %\VignetteEngine{knitr::rmarkdown} as suggested in the comments by #R18.
Now the vignette is properly built when I click on Install and Restart in RStudio.
However, checking the package still does not work. See my EDIT to the question. But this in another question: R package: Adding a vignette causes 'undefined exports'