Try it both ways. In my case the o's were zeros. If you're having issues with the website, try a different browser, like Firefox or something, but I used Edge with zero problems, but had to enter my serial number a few times to figure out the o's were zeros. And Asus doesn't really have a support team, they're really just like dealing with a customer service department. I know, because I've talked to a few of them, and their way of solving problems are the hard way. They wanted me to RMA a motherboard that wouldn't post, but all it was was the fact that I couldn't short-circuit the board, to release it, because my screwdriver was made of a weird metal and wouldn't short it, so they told me to RMA the board, so I tried some scissors and it short-circuited it, and I got it back up, finally, so I called to ask if they were having issues with the short-circuiting, and they told me no, but in their manual it says use a screwdriver, but if it's made of a different material, it won't short it, so you have to figure something else out, and I've never had to short-circuit a board, so this was my first time, but it was an interesting experience, and no their technical team was of no assistance, so I know what you mean. I had a short with my wires on my keyboard. I use a lab desk, and it's metal, and I routed the mouse and keyboard wires through it, and it cut into the insulation and was causing a short, so that's what happened, and it went on for a while, and I finally figured it out, but I was troubleshooting, reinstalled everything and still couldn't figure it out, and then found out I had that short rebooting my system, so that's what caused it, ended up making my board not post too, so I was having all kinds of problems, and I built and designed this system from scratch and this is my second build. I use the Rog Strix B550-F Gaming, so I don't have your board, but I understand your frustrations.
Your mobo is under warranty regardless of you entering the number, and all you have to do to get your RMA is call them. The warranty on mine is three years, but I will never use it. My last board lasted me eleven years and it's still good but has been retired. It was an MSI mobo, but boards don't die very often, or quickly. Both were gaming edition motherboards. About all I use. My early days on computers were on old office hardware, just to learn the ropes, but I try not to go over $200.00 a part, because it's worth it, so my stuff is built cheap, but I have good hardware, and a good amount of it was under that, but for a GPU I might spend more, but it depends on what is available. I have a good backlog of video cards that'll last me a while too.