Port is actually 5038.

After Installing FOP2, Apply Configuration Changes leads to:
Asterisk Manager Connection Failure Failed to connect to the Asterisk manager through port: 503

Also some of the PBX Settings are showing up as text rather than links.
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Status shows

retrieve_conf failed, config not applied
Ignore this
Reload failed because retrieve_conf encountered an error: 1
Added 13 minutes ago
(freepbx.RCONFFAIL)

Critical Error Asterisk Manager Connection Failure