No such host is known

I deployed a Flask website in my computer and connected it with Render Postgres database. The first two entries were successful but since then I keep getting this error:

sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) could not translate host name “dpg-cpk881sf7o1s73ckhobg-a” to address: No such host is known.

I haven’t changed anything from original settings I had set up.
Hope someone has an idea about a fix.

Use the ‘External Database URL’.