THANK YOU FOR YOUR SUGGESTION!!!!!!!!
Don't ask me how this worked but I placed the envelopes in the tray short side first. The WC displayed #10 envelopes so I selected it. Ran a test which resulted in the address printing wrong on the envelope. Turned the envelopes long side down and the menu displayed the #10 envelope option all of a sudden. Ran test and everything is working fine. Absolutely have no idea what the heck happened or what triggered the option window to change the choices.
Thank you for using the Support Forum. Please make sure you are loading the envelopes properly by following the instructions in this solution for loading envelopes. If the option for #10 continues to not display, please power off and then back on the machine. If the problem continues please consider contacting your support centre for further assistance.
On my Xerox WC5150 all of a sudden #10 Envelopes are not a option in ByPass tray settings. It shows envelopes but #10 is not included. It worked firne until now.??? Thanks