I've been using DESeq2 (v1.14.1) for some time (in R v3.3.3 on Mac OS 10.10.5), but now get following error when loading DESeq2 :

Error in library.dynam(lib, package, package.lib) : 
  shared object ‘stringi.so’ not found
Error: package or namespace load failed for ‘DESeq2’
starting httpd help server ... done

I re-installed the package but get same error. I have not recently updated my OS or R version. Would appreciate advice. Thx.

We don't support old versions of software, and your version is quite old. You need to upgrade to R-3.6.1, and then follow the installation instructions.