bibliography stopped working

Question

I am fairly new to Latex. I have googled that and saw 300 different responses and not really helped me.

My text was compiling previously with no major issues but now all my bibliography references are appearing like the label in the bib file.

I deleted the aux file due to one of the posts I saw, maybe that's the reason.

This is how it appears: "...specially in coastal zones (guannel16)."

My file header looks like that:

\documentclass[12pt, letterpaper]{article}
\usepackage[a4paper,left=2.54cm,right=2.54cm,top=1.25cm,bottom=1.5cm] 
{geometry}
\usepackage[utf8]{inputenc}%codification of the document
\usepackage[english]{babel}
\usepackage{blindtext}
\usepackage{pdfpages}
\usepackage{graphicx}
\usepackage{multirow}
\usepackage{tabularx}
\usepackage[section]{placeins}

\usepackage[autocite=inline, maxbibnames=20, citestyle=authoryear,                         
bibstyle=authoryear, backend=biber, natbib]{biblatex}
\renewcommand*{\nameyeardelim}{\addcomma\space}
\renewcommand{\thesection}{\Alph{section}}

\addbibresource{referenceRP.bib}

And the output is all citation (...) undefined.