Hp 4350 envelopes are blank

If the same fault occurs with different printers it is almost certainly caused by the document.
"...second envelope from same document" suggests you are using a mail-merger. Is that right?
What happens if you start again from scratch? Mke a new document and try to print it a a single entity, without using mail merge?

are you using the manual feed tray? If not try that as a solution.

There may be a problem with the print driver. Try deleting the printer from your computer and then re-adding it. Print driver can be downloaded at www.hp.com. in case you have lost your installation CD. Good luck !

put in envelops in the Manual Feed tray

In the paper-handling menu set the envelope feeder size to the size of your envelope and the envelope feeder type to *any type.

Then ensure you are printing envelopes from your application.

Is this affecting performance? Try new firmware. www.hp.com/go/lj4350_software.

Table 3-7. Paper Handling Menu
Item Values Explanation
ENVELOPE FEEDER
SIZE=COM10
For supported paper sizes
see page 1-12.
This item appears only when the
optional envelope feeder is installed.
Set the value to correspond with the
envelope size currently loaded in the
envelope feeder.
ENVELOPE FEEDER
TYPE=PLAIN
For supported paper types
see page 1-12.
This item appears only when the
optional envelope feeder is installed.
Set the value to correspond with the
envelope type currently loaded in the
envelope feeder.
TRAY 1 MODE=
FIRST
FIRST
CASSETTE
Determine how the printer will use
Tray 1.
FIRST: If paper is loaded in Tray 1,
the printer will pull paper from that
tray first.
CASSETTE: A paper size must be
assigned to Tray 1 using the
TRAY 1 SIZE option (the next item
in this menu when TRAY 1
MODE=CASSETTE). This allows Tray 1
to be used as a reserved tray.
TRAY 1 SIZE=
LETTER
For supported paper sizes
see page 1-12.
This item appears only when TRAY 1
MODE= CASSETTE. Set the value to
correspond with the paper size
currently

Installed SR-3 from Office Word. It did the trick.

I think it's been left open and has collected some fluff and dust, It needs a good clean. Just maybe there's a Toner Printer Cartridge leak.

This is laser scanner error message. The document is not being read from the data being sent. This could be a loose or damaged cable or bad scanner assembly. You can open it up and look for loose cables or connections to the board but otherwise if the scanner assembly is bad, it may require replacement. This should only be accomplished by a service professional as it is not a user serviceable problem.