title: Package ‘XXX’ was installed before R 4.0.0: please re-install it
body: <p>I am using R 4.0.2.</p>
  <p>I manually installed 2 packages from <code>cfcdae</code> and <code>Stats5303lib</code> from <a href="http://users.stat.umn.edu/%7Egary/classes/5303/software.html" rel="noreferrer">here</a>. I followed the instruction <a href="https://cran.r-project.org/bin/windows/Rtools/" rel="noreferrer">here</a> to download Rtools and use it to install packages above.</p>
  <p>Problem is</p>
  <pre><code>writeLines('PATH=&quot;${RTOOLS40_HOME}\\usr\\bin;${PATH}&quot;', con = &quot;~/.Renviron&quot;) # runs fine
  Sys.which(&quot;make&quot;) #works fine
                                 make 
  &quot;C:\\rtools40\\usr\\bin\\make.exe&quot; 
  install.packages(&quot;Stat5303libs_0.7-5.zip&quot;,repos=NULL,type=&quot;source&quot;) # these all run fine
  install.packages(&quot;cfcdae_0.8-4.zip&quot;,repos=NULL,type=&quot;source&quot;)  # these all run fine
  </code></pre>
  <p>However, when I ran into problem below when I tried to run the libraries.</p>
  <pre><code>Error: package or namespace load failed for ‘cfcdae’:
   package ‘cfcdae’ was installed before R 4.0.0: please re-install it
  </code></pre>
  <p>I tried below but still in vain.</p>
  <pre><code>update.packages(ask=FALSE, checkBuilt=TRUE)
  </code></pre>
  <p>Why is this happening? Is it because the package is too old?</p>
  <p><strong>Update:</strong></p>
  <p>As requested, i have changed my <code>.libPaths()</code> as below and updated the <code>SessionInfo()</code> as well.</p>
  <pre><code>&gt; .libPaths()
  [1] &quot;C:/Users/UserME/Documents/R/win-library/4.0&quot;
  [2] &quot;C:/Program Files/R/R-4.0.2/library&quot;   
  
  R version 4.0.2 (2020-06-22)
  Platform: x86_64-w64-mingw32/x64 (64-bit)
  Running under: Windows 10 x64 (build 18363)
  
  Matrix products: default
  
  locale:
  [1] LC_COLLATE=English_Hong Kong SAR.1252  LC_CTYPE=English_Hong Kong SAR.1252   
  [3] LC_MONETARY=English_Hong Kong SAR.1252 LC_NUMERIC=C                          
  [5] LC_TIME=English_Hong Kong SAR.1252    
  
  attached base packages:
  [1] stats     graphics  grDevices utils     datasets  methods   base     
  
  loaded via a namespace (and not attached):
   [1] Rcpp_1.0.4.6        rstudioapi_0.11     magrittr_1.5       
   [4] splines_4.0.2       MASS_7.3-51.6       tidyselect_1.1.0   
   [7] munsell_0.5.0       statmod_1.4.34      lattice_0.20-41    
  [10] colorspace_1.4-1    R6_2.4.1            rlang_0.4.6        
  [13] minqa_1.2.4         dplyr_1.0.0         tools_4.0.2        
  [16] grid_4.0.2          nlme_3.1-148        gtable_0.3.0       
  [19] ellipsis_0.3.1      lme4_1.1-23         tibble_3.0.1       
  [22] lifecycle_0.2.0     numDeriv_2016.8-1.1 crayon_1.3.4       
  [25] Matrix_1.2-18       nloptr_1.2.2.2      purrr_0.3.4        
  [28] ggplot2_3.3.2       vctrs_0.3.1         glue_1.4.1         
  [31] compiler_4.0.2      pillar_1.4.6        generics_0.0.2     
  [34] scales_1.1.1        boot_1.3-25         lmerTest_3.1-2     
  [37] pkgconfig_2.0.3  
  </code></pre>