If i view the book demo on github, the intro chapter (first paragraph) shows links to chapter 2 and 4 using the {#label} @ref(label) pairings.

However if i clone the repo and build the book locally i observe ?? in place of the links to the chapters.

In addition i get the following error when building the book:
1: The label(s) intro, methods not found
2: The label(s) intro, methods not found

Why would this happen?

sessionInfo:
R version 3.6.1 (2019-07-05)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 17763)

Matrix products: default

locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252

attached base packages:
[1] stats graphics grDevices utils
[5] datasets methods base

loaded via a namespace (and not attached):
[1] compiler_3.6.1 bookdown_0.14
[3] rsconnect_0.8.16 htmltools_0.3.6
[5] tools_3.6.1 yaml_2.2.0
[7] Rcpp_1.0.2 rmarkdown_2.1
[9] knitr_1.24 xfun_0.9
[11] digest_0.6.20 packrat_0.5.0
[13] evaluate_0.14