So, I can't edit my characters. I have seen other people say it's cause of a space or special character in my name but that's not the answer for me, unless it can't handle numbers.

(Well, now that I think about it that might be the problem... idk.)

So basically I used all of the character slots and now I can't edit or delete them. If I try to delete them it just loads and stops. Then if I say, try to delete their class or something, it says that they rolled a one on their api check.

If someone could help me find a solution to this problem, that would be amazing! Thank you for all who respond.

And now that I thought about it, how would I change my username?

There's a  thread in the bugs and support forum for changing your username, but that's unlikely to be the cause.

Have you tried it on another device, or another browser, or in a incognito tab on your browser?

If it works there, you can likely fix it by telling your browser to delete the cookies and cached data for the site.

Do you have any browser extensions, particularly ones that interact with DDB?

You can also try contacting support, but they're likely to step you through the same debugging steps first.

I have dndbeyond usually on chrome, so i tried it on microsoft edge and that didn't work.
I'll try it on an incognito tab.
I do have browser extensions on chrome but none of them specifically are for dndbeyond, and the problems were there before I started using them.

Incognito didn't work.

Might want to try Firefox. Edge is Chromium-based, might cause the same issues within the same system. Also could try a different device (such as a cell phone's browser) to see if it's the device causing the issue.