If the compiled myarticle.tex originally used a very large biblio.bib file, perhaps containing your entire paper repository gulp then this is often too large for your coauthors and too large for Overleaf. The solution is to use the command below to output just the .bib entries that are called during the compilation of myarticle.tex. The new .bib will be called extracted.bib.
bibexport -o extracted.bib myarticle.aux