If a project contains online layers (PostGIS, WMS, WFS, etc), QFieldCloud will try to establish a connection to this services. Sometimes these services are behind a firewall and the system administrators need to allowlist the QFieldCloud IP.
If your project contains PostgreSQL (PostGIS) layers, you need to configure your PostgreSQL server so it allows connection from
app.qfield.cloud IP address.
Otherwise, you will get an error like this:
FATAL: no pg_hba.conf entry for host "188.8.131.52", user "qfc", database "mydb_test", SSL off WARNING:QGIS_MSGLOG:1 unavailable layer(s) found:
To do so, you need to edit the
pg_hba.conf file where your PostgreSQL server is hosted. For more information, refer to recommendations on StackOverflow questions.