Hi
Thanks for stopping by the HP Support Forums! I read about the printer issue and wanted to stop in to share my suggestions with you.
Going through your post, it looks like you purchased new Envy 4520 printer and is having difficulty while printing different paper sizes and envelopes. I think you need to try and change some of the paper settings to get this machine working fine for you. Also, you can find all the support documents from here: https://support.hp.com/us-en/product/hp-envy-4520-all-in-one-printer-series/5447920/how-to
Alternatively, try the below-mentioned link to change the paper settings to print documents and envelopes.
To change print settings in MAC OS: HP Printers - Print Driver Settings Guide (Mac)
Printing envelopes in MAC OS: HP Printers - Printing Envelopes (Mac)
HP Printers - Printing Documents (Mac)
Please let me know if this resolves the issue, or if you require further assistance.
Feel free to post your query for any other assistance as well,
It's been a pleasure interacting with you and I hope you have a good day ahead.
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Regards,