Fix Envelope & Label Alignment Printing

My HP OfficeJet 8710 refuses to place the mailing address in the middle of my pre-cut envelopes and label sheets—the text keeps drifting off-centre. I need someone who can quickly diagnose the reason, create or adjust the correct print template, and walk me through any printer driver or page-setup tweaks so everything lands perfectly centred every time.

Acceptance criteria:
• Addresses print dead-centre on both my special envelopes and label stock.
• Clear, written instructions/template delivered for reuse.