Why does the fax on the HP MFP not receive outside and accept from internal numbers (Avaya IP Office 500 PBX)?

Question

Avaya

Actually, the topic says it all - there is an MFP from HP, it perfectly accepts faxes sent to an internal number, however, with a direct call to an internal number and sending, everything is printed out perfectly.
The trick with a call to a direct line and forwarding through another internal one does not work, apparently the matter is in the line, but in Manager there are no restrictions on the connection time.
Where to look, please advise.